The name says it all, this is the unofficial Internet lingo thread/dictionary
Feel free to add any acronyms you know, and arent listed here.

Acronyms: Here and Back.
AFK: Away from keyboard
BAK: Back at keyboard
BFN: Bye for now
Variations: B4N, BBL (be back later).
BRB: Be right back
CU: See you
The more formal version of cya (See ya).
LTNS: Long time, no see
TTFN: Ta ta for now
L8tr: Later.
GAL:l Get a life
KISS: Keep it simple, stupid
PU: That stinks
TSWC: Tell someone who cares
GFETE: Grinning from ear to ear.
LMAO: Laughing my ass off.
LOL: Laugh out Loud
ROTFL: Rolling on the floor laughing.
AAMOF: As a matter of fact.
AFAIK: As for as I know
BTW: By the way
DAMHIKT: Dont ask me how I know this
EOD: End of discussion
HTH: Hope that Helps
IMHO: In my humble opinion
IANALB: Im not a lawyer, But...
J/K: Joking/ Kidding
OT: Off topic
OTOH: On the other hand.
AIAMU: And im a monkeys uncle.
CMF: Count my fingers
DGT: Dont go there
TMI: To much information
MMD: Make my Day.
: ) Smile
: ( Frown
; ) Wink
: o Shocked
?-( Black eye
: P Funny

[i]Added!
LMFAO- Laughing my fucking ass off
IIRC- If I remember correctly
GTG- Got to go
TTYL- Talk to you later
w/e: whatever
w/o: without
WTF: what the fuck?