Came across these...

> ^5 - High Five
> addy - address (as in eMail)
> ADN - Any Day Now
> AFAIK - As Far As I Know
> AFK - Away From Keyboard
> AKA - Also Known As (also a/k/a)
> ARE - Acronym-Rich Environment
> ATM - According To Me
> ATTN - Attention
> BAK - Back At the Keyboard
> BBIAB - Be Back In A Bit
> BBL - Be Back Later
> BBS - Be Back Soon
>  - Big Evil Grin
> BFD - Big F***ing Deal
> BFN - Bye For Now (also B4N)
>  - big grin
> BIF - Basis In Fact
> BION - Believe It Or Not
> BIOYIOP - Blow It Out Your I/O Port
> BL - Belly Laughing
> BRB - Be Right Back
> BTA - But Then Again...
> BTSOOM - Beats The Sh*t Out Of Me
> BTW - By The Way
> CU - see you
> CUA - Commonly Used Acronym(s) or Common User Access
> CUL - see you Later (also CUL8ER)
> CWYL - Chat With Ya Later
> CYA - see Ya or Cover Your A**
> CYO - see You Online
> DBA - Doing Business As (also d/b/a)
> DFLA - Disenhanced Four-Letter Acronym (that is, a TLA)
> DIKU - Do I Know You?
> DITYID - Did I Tell You I'm Distressed?
> DTRT - Do The Right Thing
>  - Evil Grin
> EMFBI - Excuse Me For Butting In
> EOM - End Of Message (no comments)
> EOT - End Of Thread (end of discussion)
> ETLA - Enhanced Three-Letter Acronym (that is, an FLA)
> F2F - Face to Face
> FAQ - (list of) Frequently Asked Question(s)
> FISH - First In, Still Here
> FLA - Four-Letter Acronym
> FOMCL - Falling Off My Chair Laughing
> FUBAR - F*cked Up Beyond All Recognition
> FUD - (spreading) Fear, Uncertainty & Doubt
> FWIW - For What It's Worth
> FYA - For Your Amusement
> FYEO - For Your Eyes Only
> FYI - For Your Information
>  - grin ( - big grin)
> GA - Go Ahead
> GAL - Get A Life!
> GIGO - Garbage In, Garbage Out
> GIWIST - Gee, I Wish I'd Said That!
> GMTA - Great Minds Think Alike
> GOL - Giggling Out Loud
> GR&D - Grinning, Running & Ducking
> GTRM - Going To Read Mail
> HHOK - Ha Ha, Only Kidding
> HHOS - Ha Ha, Only Serious
> HNG - Horny Net Geek
> HTD - Have To Disagree...
> HTH - Hope This Helps
> HTHBE - Hope This Has Been Enlightening
> IAC - In Any Case
> IAE - In Any Event
> IANAL - I Am Not A Lawyer, but... (also IANAxxx, such as IANACPA)
> IC - I see
> ICAM - I Couldn't Agree More
> ICOWHMGOWYHH - I Can Only Wonder How Many Glasses Of Wine You Have Had
> ID - I Disagree
> IHA - I Hate Acronyms
> IIRC - If I Remember Correctly
> ILY - I Love You (also ILU)
> IMAO - In My Arrogant Opinion
> IMCO - In My Considered Opinion
> IMHO - In My Humble Opinion
> IMNSHO - In My Not-So-Humble Opinion
> IMO - In My Opinion
> INC - Illegitimi Non Carborundum (Latin: don't let the b*stards wear you
> down)
> IOW - In Other Words
> IPN - I'm Posting Naked
> IRL - In Real Life (that is, when not chatting)
> IRT - In Real Time
> ITA - I Totally Agree!
> ITRW - In The Real World
> JAT - Just A Thought
> JFU - Just For You
> JIC - Just In Case
> JK - Just Kidding (also j/k)
> JMHO - Just My Humble Opinion
> JMO - Just My Opinion
> KWIM? - Know What I Mean?
> L8R - Later (also L8TR)
> LBAY - Laughing Back At You
> LD - Later, Dude
> LDR - Long-Distance Relationship
> LLTA - Lots and Lots of Thunderous Applause
> LMAO - Lauging My Ass Off
> LOL - Laughing Out Loud or Lots Of Luck
> LOLBAY - Laughing Out Loud Back At You
> LTM - Laugh To Myself
> LTNS - Long Time, No See
> M/F? - Male or Female? (also MorF)
> MEGO - My Eyes Glazed Over (booorrring)
> MHOTY - My Hat's Off To You
> MINK - Multiple Income, No Kids (NIMK?)
> mm - merrily met (greeting)
> MMHA2U - My Most Humble Apologies to you
> MOOS - Member Of the Opposite Sex (also MOTOS)
> MOSS - Member Of the Same Sex (also MOTSS)
> MOTD - Message Of The Day
> mp - merrily parted (farewell)
> MUD - Multi-User Dungeon (or Dimension)
> NBIF - No Basis In Fact
> NBIR - No Basis In Reality (where am I; is this Kansas?)
> NFW - No F*cking Way
> NP - No Problem
> NRN - No Reply Necessary
> NS - 'Nuff Said
> OIC - Oh, I see
> OLL - On-Line Love
> OMG - Oh My God!
> OOTB - Out Of The Box (brand new, ready to roll)
> OPM - Other People's Money
> OTF - On The Floor
> OTOH - On The Other Hand
> OTOOH - On The Other, Other Hand
> OTP - On The Phone
> OTTH - On The Third Hand
> OTTOMH - Off The Top Of My Head
> ::POOF:: - goodbye (leaving the chatroom)
> PANS - Pretty Awesome New Stuff (as opposed to POTS)
> PC - Politically Correct (or Personal Computer)
> PCMCIA - People Can't Master Computer Industry Acronyms (Personal
> Computer Memory Card Int'l. Ass'n.)
> PDA - Public Display of Affection
> PDQ - Pretty Darn Quick
> PEBCAK - Problem Exists Between Chair And Keyboard
> PI or PIC - Politically Incorrect
> PITA - Pain In The A**
> PMFJI - Pardon Me For Jumping In (but eventually, you'll thank me)
> PMJI - Pardon My Jumping In
> POTS - Plain Old Telephone Service (or Pretty Old Tired Stuff)
> POV - Point Of View
> PPL - Peed Pants Laughing or People
> PU - that stinks!
> PUTS - Playing Under The Sofa
> r - are
> re - regarding or hello again
> RL - Real Life (that is, when not chatting)
> ROAR! - laughing as loud as a lion
> ROFL - Rolling On Floor, Laughing (also ROF,L)
> ROTFLMAOWPIMP - Rolling On The Floor, Laughing My A** Off, While Peeing
> In My Pants
> ROTFLMBHO - Rolling On The Floor Laughing My Bloody Head Off
> ROTFLMBO - Rolling On The Floor, Laughing My Butt Off
> RP - Romantic Partner
> RPG - Role-Playing Games
> RSN - Real Soon Now (often ironic)
> RTFM - Read The F*cking Manual (or Message)
> RW - Real World (outside cyberspace)
> RYO - Roll Your Own (write your own program)
>  - Sh*t-Eating Grin
> SHOUTING - Not an acronym; it's bad netiquette to leave Caps Lock on.
> SHOUTING IS HARD TO READ.
> SINK - Single Income, No Kids
> SITD - Still In The Dark
> sm - smiley
> SNAFU - Situation Normal, All F*cked Up
> SO - Significant Other
> SOL - Smiling Out Loud or Sadly, Outta Luck (really, there's another
> version?!)
> SOMY - Sick Of Me Yet?
> STD - Sick To Death (a term of disdain, rather than an update on the
> author's well-being)
> STS - Sorry To Say
> TAF - That's All, Folks!
> TAFN - That's All For Now
> TANSTAAFL - There Ain't No Such Thing As A Free Lunch
> TAT - Tête-A-Tête
> TCN - Take Care Now
> TFH - Thread From Hell (a discussion that just won't die)
> TFI - The Fact Is ...
> TFM - Thanks From Me
> TFMT - Thanks From Me, Too!
> TGIF - Thank God It's Friday
> THX - Thanks
> TIA - Thanks In Advance
> TIC - Tongue In Cheek
> TIG - This Is Great!
> TIIC - The Idiots In Charge
> TLA - Three-Letter Acronym (such as this)
> TPTB - The Powers That Be
> TTFN - Ta Ta For Now
> TTYL - Talk To You Later (or TLK2UL8R or TYL)
> TXS - Thanks! (sincere and heartfelt - really!)
> TYSM - Thank You So Much
> TYVM - Thank You Very Much
> u - you
> UAPITA - You're A Pain In The A**
> unPC - Politically Incorrect
>  - very big grin
>  - Very Big Sh*t-Eating Grin
> VWP - Very Well Put
> W4W - Word for Word
> WAGS - What A Great Story!
> WAI - What An Inspiration!
> WB - Welcome Back
> WDALYIC - Who Died And Left You In Charge?
> WFM - Works For Me
> WIBNI - Wouldn't It Be Nice If...
> WP - Well Put
> WT? - What/Who The...?
> WTFO - What The F*ck? - Over!
> WTG - Way To Go
> WTGP? - Want To Go Private?
> WTS - With That Said
> WU? - What's Up?
> WUF? - Where are you From?
> WYSIWYG - What You See Is What You Get
> XOXO - kisses and hugs
> XX - kisses
> Y2K - Year 2000 calendar concerns
> YAAG - You Are A Genius
> YABR - You Are Being Replaced
> YGBSM - You've Gotta Be Sh*ttin' Me!
> YMMV - Your Mileage May Vary
> YRR - You 'R' Right (I give...)
> YVMW - You're Very Much Welcome

Source here.