With many Internet Service Providers charging by the hour, and with telephone charges being as high as they are, TLA's have become increasingly popular. They save time typing, therefore saving costly charges.
This list may not be all of them (some have been omitted on purpose!) but it will give you a head start.
<G> Grin AFAICT As Far As I Can Tell AFAIK As Far As I Know AFK Away From Keyboard AIUI As I Understand It B4 Before BAK Back At Keyboard BBL Be Back Later BCNU Be Seeing You BRB Be Right Back BSF But Seriously Folks BTDT Been There, Done That BTSOOM Beats The **** Out Of Me BTW By The Way BWQ Buzz Word Quotient CLM Career Limiting Move CUL See You Later DWIM Do What I Mean DWISNWID Do What I Say Not What I Do DYJHIW Don’t You Just Hate It When EOF End Of File ESAD *Insult* ETLA Extended Three Letter Acronym F2F Face To Face FAQ Frequently Asked Questions FGS For Goodness Sake FOAD *Insult* FOAF Friend Of A Friend FOC Free Of Charge FUBAR ‘Messed’ Up Beyond All Recognition FWIW For What It’s Worth FYA For Your Amusement FYE For Your Entertainment FYI For Your Information GA Go Ahead GAL Get A Life GIGO Garbage In, Garbage Out GR&D Grinning, Running And Ducking HHOJ Ha Ha, Only Joking HHOS Ha Ha, Only Serious IAE In Any Event IANAL I Am Not A Lawyer IIRC If I Recall Correctly IME In My Experience IMHO In My Humble Opinion IMO In My Opinion IOW In Other Words IRL In Real Life ISTM It Seems To Me ISTR I Seem To Recall ITRO In The Region Of ITRW In The Real World IWBNI It Would Be Nice If IYSWIM If You See What I Mean JAM Just A Minute KISS Keep It Simple, Stupid L8R Later LOL Laugh Out Loud MORF Male Or Female? MOTAS Member Of The Appropriate Sex MOTOS Member Of The Opposite Sex MOTSS Member Of The Same Sex MUG Multi User Game NALOPKT Not A Lot Of People Know That NIFOC Nude In Front Of Computer NRN No Reply Necessary NWM No Way Man! OAO Over And Out OBTW Oh, By The Way OEM Original Equipment Manufacturer OIC Oh, I See OMG Oh My God! OTOH On The Other Hand OTT Over The Top PD Public Domain PITA Pain In The ‘Bottom’ POD Piece Of Data RFD Request For Discussion ROFL Rolls On Floor Laughing RSN Real Soon Now RTFAQ Read The FAQ RTFM Read The Flipping Manual RUOK Are You Ok SITD Still In The Dark SMOP Small Matter Of Programming SNAFU Situation Normal, All ‘Messed’ Up SNR Signal To Noise Ratio SO Significant Other STFU Shut *** **** Up TANSTAAFL There Ain’t No Such Thing As A Free Lunch TCB Trouble Came Back TDM Too Damn Many TIA Thanks In Advance TIA Thanks In Advance TIC Tongue In Cheek TLA Three Letter Acronym TNX Thanks TPTB The Powers That Be TTFN Ta Ta For Now TTYL Talk To You Later TVM Thanks Very Much UBD User Brain Damage VC Virtual Community VR Virtual Reality WIBNI Would Be Nice If WRT With Regard To WTH What The Hell WYSIWYG What You See Is What You Get YABA Yet Another Bloody Acronym YHM You Have Mail