I don't use most of these, so I have to look them up when someone else uses an obscure one.

Abbrev.	Meaning
AAMOF	As a matter of fact
AFAIK	As far as I know
BAC	By any chance
B4	Before
B4N	Bye for now
BTW	By the way
CMIIW	Correct me if I'm wrong
CUL	See you later
EOF	End of file
FITB	Fill in the blank
4U	For you
F2F	face-to-face
FWIW	For what it's worth
HAND	Have a nice day
HHOK	Ha-ha just kidding
HTH	Hope this helps
IAC	In any case
ICCL	I couldn�t care less
IDK	I don�t know
IKWUM	I know what you mean
IMHO	In my humble opinion
IMO	In my opinion
IOW	In other words
IYKWIM	If you know what I mean
JM2C	Just my two cents
KWIM	Know what I mean
LMAO	Laughing my ass off
LOL	Laughing out loud
NBIF	No basis in fact
NN2R	No need to reply
OTOH	On the other hand
ROTFL	Rolling on the floor laughing
RTFM	Read the f****** manual
SICS	Sitting in chair snickering
TIA	Thanks in advance
TNX	Thanks
TTFN	Ta-ta for now
2L8	Too late
2U	To you
YWIA	You're welcome in advance

* I did NOT make any of this up, so if you think any part of this is absurd, don't come complaining to me.