2U2            to you, too

A
AAMOF          As A Matter Of Fact
ADN            Any Day Now
AFAIK          As Far As I Know
AFK            Away From Keyboard
AFU            All Fucked Up
AKA            Also Known As
AMF            Adios, MotherFucker!
ASAP           As Soon As Possible
AOL            Army Of Lamers
ATM            At The Moment
AWGTHTGTTA?    Are We Going To Have To Go Through This Again?

B
B4N            Bye for Now
BAC            By Any Chance
BAK            Back At Keyboard
BAMF           Bad Assed Mother Fucker
BBFN           Bye Bye For Now
BBR            Burnt Beyond Repair
BFN            Bye For Now
BBL            Be Back Later
BCNU           Be Seeing You
BFH            Big Fucking Hammer
BFN            Bye For Now
BIOYA          Blow It Out Your Ass
BIOYIOP        Blow It Out Your I/O Port
BOT            Back On Topic
BRB            Be Right Back
BTA            But Then Again (in response to IOW)
BTDTGTS        Been There, Done That, Got the T-Shirt
BTW            By The Way
BYKT           But You Know That

C
C4N            Ciao for Now
CFD            Call For Discussion
CFV            Call For Vote
CMIIW          Correct Me If I'm Wrong
CRAFT          Can't Remember A Fucking Thing
CU             see you
CUL(8R)        see you later
CYA            see ya (also: Cover Your Ass)

D
D-C            Don't Care
DAMIFINO       Damn If I know
DARFC          Ducking And Running For Cover
DFL            Dead Fucking Last
DH             Dear Husband (also Dear Hubby, Duh Hubby and of course Dick Head) 
DIIK           Damned If I Know
DILLIGAF?      Do I Look Like I Give A Fuck? Does It Look Like I Give A Fuck? 
DIY            Do It Yourself
DOM            Dirty Old Man
DTRT           Do The Right Thing
DWIM(C)        Do What I Mean (, Correctly)
DYJHIW         Don't You Just Hate It When...
DYK            Do You Know
DYT            Do You Think

E
EFN (E4N)      Enough For Now
eg             Evil Grin
EOD            End Of Discussion
EOF            End Of File
EOL            End Of Lecture
EOT            End Of Transmission / End Of Thread (i.e., don't reply to this message)
ESAD  (ES&D)   Eat Shit and Die
ESADMF         Eat Shit and Die Mother Fucker
ETLA           Extended Three Letter Acronym

F
F2F (FTF)      Face-To-Face (as IRL) / Flesh To Flesh
FAQ            Frequently Asked Questions
FETLA          Further Extended Three Letter Acronym (ie it has five letters.)
FOAD           Fuck Off And Die
FISH           First In, Still Here
FITB           Fill In The Blank_________
FOAF           Friend Of A Friend
FOOBAR         Variant of FUBAR (q.v.)
FOS            Freedom Of Speech. Also Full Of Shit
FRED           Fucking Ridiculous Electronic Device
FTTT           From Time To Time
FU             Fucked Up
FUBAB          Fucked Up Beyond All Belief
FUBAR          Fucked Up Beyond All Reason/Recognition/Repair
FUD            Fear, Uncertainty and Doubt
FURTB          Full Up Ready To Burst (about hard disk drives!)
FWIW           For What It's Worth
FY&TSYRIO      Fuck You And The Sysop You Rode In On
FYA            For Your Amusement
FYDITM         Fuck You Directly In The Mouth
FYI            For Your Information

G
G              Grin (as in <g>)
GA             Go Ahead
GAFIA          Get Away From It All
GAL            Get A Life
gbh            Great Back Hug
gbh&k          Great Back Hug & Kiss
gd&r           Grinning, Ducking And Running
gd&rf          Grinning, Ducking And Running FAST!
gd&rvvf        Grinning, Ducking And Running VERY VERY FAST!
gd&w           Grinning, Ducking And Weaving
GFC            Going For Coffee
GH             Getting Hard (q.v. GW)
GIGO           Garbage In, Garbage Out
GIWIST         Gee, I Wish I'd Said That
GLGH           Good Luck and Good Hunting
GMTA           Great Minds Think Alike
GOK            God Only Knows
gr&d           Grinning, Running & Ducking
GRMBL          grumble
GTG            Got To Go
GW             Getting Wet (q.v. GH)

H
h              Hug
HAND           Have A Nice Day
hb             Hug Back
hh             Holding Hands
HHOJ           Ha Ha Only Joking
HHOK           Ha Ha Only Kidding
HHOS           Ha Ha Only Serious
HIWTH          Hate It When That Happens
HMOFG (HMFG)   Holy Mother Of Fucking God.
HTH            Hope This Helps

I
IAC            In Any Case
IAE            In Any Event
IANAL          I Am Not A Lawyer
IAP            It's A Possibility
IC             I See
ICBW           I Could Be Wrong
IDGI           I don't get it
IDK            I don't know
IDM2M          it doesn't matter to me
IDTT           I'll Drink To That!
IHTFP          I have truly found paradise / I hate this f'n place
IIRC           If I Recall Correctly
IITYWIMIWHTKY  If I tell you what it means, I will have to kill you
IITYWIMWYBMAD  If I tell you what it means, will you buy me a drink?
ILY            I Love You
IMAO           In My Arrogant Opinion
IMCO           In My Considered Opinion
IME            In My Experience
IMHO           In My Humble Opinion
IMnerHO        In My Not Even Remotely Humble Opinion
IMNSHO         In My Not So Humble Opinion
IMO            In My Opinion
IMOBO          In My Own Biased Opinion
IMPE           In My Previous/Personal Experience
INAP           It's Not A Possibility
INPO           In No Particular Order
IMVHO          In My Very Humble Opinion
IOW            In Other Words
IRL            In Real Life
ISTR           I Seem To Recall
ISWYM          I See What You Mean
IWBNI          It Would Be Nice If
IYFEG          Insert Your Favorite Ethnic Group
IYKWIM         If You Know What I Mean
IYKWIMAITYD    If You Know What I Mean And I Think You Do
IYTS           If You Think So

J
J4F            Just For Fun
JASE           Just Another System Error
J/K            Just Kidding (can also stand for joking)
JIC            Just In Case
JM2C           Just My 2 Cents
JS             just Smile
JSNM           Just Stark Naked Magic
JTYWTK         Just Thought You Wanted To Know

K
k              Kiss
kb             Kiss Back
KISS           Keep It Short And Simple / Keep It Simple Stupid
KMYF           Kiss Me You Fool
kotc           Kiss On The Cheek

L
l              Laugh
L8R            Later
LAB&TYD        Life's A Bitch & Then You Die.
LAGNAF         Let's All Get Naked And Fuck!
LART           Luser Attitude Readjustment Tool
li             Laughing Inside
lis            Laughing In Silence
LLTA           Lots and Lots of Thunderous Applause
LMAO           Laughing My Ass Off
lmbo           Laughing My Butt Off
LMWIS          Lick Me Where I Sweat
LOL            Laughing Out Loud

M
MfG            Mit freundlichen Gruessen
MHBFY          My Heart Bleeds For You
MHOTY          My Hat's Off To You
MLA            Multiple Letter Acronym
MORF           Male or Female
MOTAS          Member Of The Appropriate Sex
MOTOS          Member Of The Opposite Sex
MOTSS          Member Of The Same Sex
MYOB           Mind Your Own Business

N
NBL            Not Bloody Likely
NC             No Comment
NFW            No Fucking Way
NHOH           Never Heard Of Him (Her)
NIFOC          Naked/Nekkid In Front Of Computer
NIMBY          Not In My Backyard
NN2R           No Need To Reply
NRN            No Reply Necessary
NTP            New Topic, Please
NYCTMI         Now You Come To Mention It

O
OBTW           Oh, By The Way
OIC            Oh, I See
OK             Oll Korrect (all correct : al)
OnJo           only joking
ONNA           Oh No, Not Again!
OOI            Out Of Interest
OOTB           Out Of The Box (brand new)
OOTC           Obligatory On-Topic Comment
OT             Off topic
OTF            On The Floor
OTOH           On The Other Hand
OTTH           On The Third Hand

P
PABG           Pack a Big Gun
PDA            Public Display of Affection
PCMCIA         People Can't Memorize Computer Industry Acronyms
PCYLIHOONL     Please Cross Your Legs, I Have Only One Nail Left
PDQ            Pretty Damn(ed) Quick(ly)
PITA           Pain In The Ass
PLOKTA         Press Lots Of Keys To Abort
PMBI           Pardon My Butting In
PMETC          Pardon Me ETC 
PMFBI          Pardon Me For Butting In
PMJI           Pardon Me, Jumping In (when you interrupt a conversation)
PMFJI          Pardon Me For Jumping In
POSSLQ         Person of Opposite Sex Sharing Living Quarters
POV            Point Of View
PTB            Powers That Be

R
RE             Regarding
REHI           hello again (re-Hi!)
RFC            Request For Comment
RFD            Request For Discussion
RO(T)FL        Rolling On The Floor Laughing
ROTFLAHMS      Rolling On The Floor Laughing And Holding My Side
ROFLMAO        Rolling On The Floor Laughing My Ass Off
RSN            Real Soon Now
ROTM           Right On The Money
RTFAQ          Read The FAQ
RTDox          Read The Documentations
RTFFAQ         Read The Fucking FAQ
RTFM           Read The Fucking Manual
RTM            Read The Manual
RUMOF          are you male or female?

S
s              Smile
sb             Smiles back
SFAIAA         So Far As I Am Aware
SFLA           Stupid Four Letter Acronym
SHIT           Sure Happy It's Thursday
SHTSI          Somebody Had To Say It
SIG            Special Interest Group
SITD           Still In The Dark
SMO            Serious Mode On
SMOP           Small Matter Of Programming
SMOff          Serious Mode Off
SNAFU          Situation Normal; All Fucked Up
SO             Significant Other (e.g. boyfriend, girlfriend, husband,  wife, pet dog)
SOB            Do you really need *me* to explain this one?
SOHF           Sense Of Humor Failure
SOS            Same Old Shit (or Stuff)
SSDD           Same Shit Different Day
SW             Shareware
SWAG           Scientific Wild Ass Guess
SWALK          Sealed With A Loving Kiss
SWMBO          She Who Must Be Obeyed
SWWCFI         So What, Who Cares, Fuck It
SYL            See You Later
SYSOP          SYStem OPerator, aka God

T
TAFN           That's All For Now
TANJ           There Ain't No Justice
TANSTAAFL      There Ain't No Such Thing As A Free Lunch (voir http://www.atnf.csiro.au/~rgooch/linux/docs/kernel-list-faq.html)
TARFU          Things Are Really Fucked Up
TCB            Trouble Came Back
TDM            Too Damn Many
TGIF           Thank God Its Friday
THX            Thanks
TIA            Thanks In Advance
TIATLG         Truly, I Am The Living God
TINALO         This Is Not A Legal Opinion
TINAR          This Is Not A Recomendation
TLA            Three Letter Acronym
TNSTAAFL       There's No Such Thing As A Free Lunch
TNX            Thanks
TNX 1.0E6      Thanks a million
TPTB           The Powers That Be
TRDMC          Tears Running Down My Cheers
TTBOMK         To The Best Of My Knowledge
TTFN           Ta-Ta For Now
TTL4N          That's The Lot For Now
TTUL           Talk (or Type) To You Later
TTYL(8R)       Talk To You Later
TWIMC          To Whom It May Concern
TYVM           Thank You Very Much

U
UCE            Unsolicited Commerical E-mail
UST            Unresolved Sexual Tension [X-Philes (fans)]

V
veg            Very evil grin
ves            Very evil smile
vwg            Very wicked grin
vws            Very wicked smile

W
w              Wink
WDYT           What Do You Think?
WFM            Works For Me
wg             Wicked grin
WIIWD          What It Is We Do
WIMP           Windows, Icons, Mouse, Pointing
WOFTAM         Waste Of Flaming Time And Money
WRT            With Regard (Respect) To
WTF            What The Fuck
WTFDIK         What The Fuck Do I Know
WTF R U ?      Who The Fuck Are You?
WTH            What The Hell
WTHDTM         What The Hell Does That Mean
WTLOB          Watch "The Life Of Brian"
WWDWIIWD       When We Do What It Is We Do
WYGIWYPF       What You Get Is What You Pay For
WYSIAYG        What You See Is All You Get
WYSIWYG        What You See Is What You Get
 
Y
YABA           Yet Another Bloody Acronym
YABSA          Yet Another Bloody Stupid Acronym
YKYBHTLW       You Know You've Been Hacking To Long When...
YGWYPF         You Get What You Pay For
YKYHBxTLW      You Know You Have Been x Too Long When
YMMV           Your Mileage May Vary
YMMVG          Your Mileage May Vary Greatly
YWIA           You're Welcome In Advance


Useful expressions

B4              before
2nite           tonight
n case          in case
EZ              easy
troo            true
kewl            cool
dewd            dude
d00d            dude
grrlz           girls
wirld           world
guvment         government
gawd            god
wymyn           women
to go nookleer  to explode
n/a             not applicable
w/              with
w/o             without
b/c (BK)        because
Xtian           Christian
wuz             was
cos(cuz)        because
w3b             www
tripdub         www ("triple w")
K               1000 (like, 2K = 2000)
@               Circle A (symbol for anarchy)
B-D             breakdown
BRS             Big Red Switch (hacker term)
BTL             Better Than Life
S&D             search and destroy
R&D             research and development
R&P             rape and pillage (excessive violence)
TAZ             temporary autonomous zone; mobile or transient
                location free of economic and social interference by
                the state. [Hakim Bey]
TBT             talking by typing
T-P             telepathy