ADN Any day now
AFAIK As Far As I Know
AFK Away From Key Board
AKA Also Known As
ASAP As Soon As Possible
A/S/L  Age/Sex/Location
BAK Back At Keyboard
BBIAB Be back in a bit
BBL Be Back Later
BCNU Be Seeing You
BEG Big evil grin
BFD Big f***ing deal
B4N Bye For Now
BRB Be Right Back
BTDT Been there, done that
BTW By The Way
F2F Face To Face
FWIW For What It's Worth
FYA For Your Amusement
FYI For Your Information
GFY Good For You
GGBB Gotta Go Bye Bye
GL Good Luck
GMTA Great Minds Think Alike
G2G Got To Go
GTGB Got To Go Bye
ILU  Love You
IDK I Don't Know
IM Instant Message
IMHO In My Humble Opinion
IMO In My Opinion
INALB I'm Not A Lawyer But
IOH I'm Outta Here
IOW In Other Words
IRL In Real Life
ITS I Told You So
KIT Keep In Touch
LOL Laughing Out Loud
LTL Lets Talk Later
LTNC Long Time No Chat
LTNS Long Time No See
LU Looking Up
MAYB  Maybe
NM Nothing Much
NP No Problem
NRN No Reply Necessary
NYO Need Your Opinion
PDQ Pretty Darn Quick
PLS Please
PMFJI Pardon Me For Jumping In
POS Parents Over Shoulder Change Subject
POV Point Of View
ROTFL Rolling On The Floor Laughing
RSN Real Soon Now
RTFM Read The "Fascinating" Manual
TIA Thanks In Advance
TMI Too Much Info
TTFN Ta Ta For Now
TTYL Talk To You Later
TTYS Talk To You Soon
TU Thank You
TX Thanks
TY Thank You
TYVM Thank You Very Much
YMMV  Your Mileage May Vary (different luck)
UKW You Know Who
U You
U2 You Too
UW You Wish
WB Welcome Back