AFAIK- As far as I know...
AFK- Away from keyboard
ATM- At The Moment
BFN- Bye For Now 
BRB- Be Right Back 
BTW- By The Way
CTTS-Cute Things They Say
DH (DW/DD/DS)- Dear Husband (dear wife/daughter/son)
FAQ- Frequently Asked Questions
FOFL- Falling On Floor Laughing
FTP- File Transfer Protocol 
FWIW- For What it's Worth
FYI- For Your Information
GAL- Get A Life
GG- Gotta Go
HAGD- Have a Great Day
HAND- Have a Nice Day
HTH- Hope This Helps
IAE- In Any Event
ICBW- I Could Be Wrong
IIRC- If I Recall Correctly
IMAO- In My Arrogant Opinion
IMHO- In My Humble Opinion
IMNSHO- In My Not So Humble Opinion
IMO- In My Opinion
IOW In Other Words 
IRL In Real Life 
ISDN It Still Does Nothing 
ISWYM I See What You Mean 
ISTR I Seem To Recall 
LMAO Laughing My A** Off 
LOL Laughing Out Loud
JMTCW Just my two cents worth
OTOH On The Other Hand 
OT Off Topic
PMFJI Pardon Me For Jumping In
ROFL Rolling on the Floor Laughing 
ROTFL Rolling On The Floor Laughing 
ROTFLMAO Rolling On the Floor, Laughing My A** Off 
RFC Request For Comment
SFAIAA So Far As I Am Aware
SFMP- Sorry For Multiple Posts
SCNR Sorry, Could Not Resist
SITD Still In The Dark
SO Significant Other
TIA Thanks In Advance 
TIC Tongue In Cheek 
TTFN Ta ta For Now 
TTYL Talk To You Later
TWIMC To Whom It May Concern 
TYVM Thank You Very Much
WYSIWYG What You See Is What You Get
YMMV-Your mileage may vary


Smileys
from: http://www.netlingo.com/smiley.cfm

@>--;-- A rose
O:-) Angel
0*-) Angel winking
d:-) Baseball
:-) Basic
:) Basic Little Kid 
(:-) Big Face 
(((H))) Big Hug 
(:-D Blabber Mouth 
:-}X Bow Tie-Wearing 
}|{ Butterfly 
})i({ Butterfly - an even prettier one
}:-X Cat
q:-) Catcher
C=:-) Chef
8^ Chicken
;-( Chin up 
*<):o) Clown
:-S Confused
H-) Cross-Eyed 
O-) Cyclops 
:-e Disappointed
:3-] Dog 
<:-l Dunce 
:") Embarrassed 
:-! Foot in Mouth
=:-H Football player 
8) Frog 
@:-} Just Back From Hairdresser
:-x Kid smiley
:-* Kiss
>^,,^< Kitty Cat
>:-l Klingon
@(*0*)@ Koala Bear
(-: Left Hand 
|-( Lost Contact Lenses
X-( Mad 
8(:-) Mickey Mouse 
P-( Pirate 
}:^#) Pointy Nosed
:-t Pouting
X:-) Propeller Head 
[:] Robot
3:*> Rudolph the red nose reindeer
:( Sad Turtle
:-d Said with a smile
*<|:-) Santa Claus 
:-@ Screaming 
:-V Shouting
~:-P Single Hair
:-/ Skeptical
;^) Smirking 
:-0 Talkative 
:-\ Undecided 
|:-) Unibrow 
(:-( Very Unhappy 
[:-) Wearing a Walkman
8-) Wearing Contacts
B-) Wearing Glasses 
:-" Whistling
'-) Winking
,-) Winking Happy
8<:-) Wizard
-=#:-) \ Wizard with Wand
,-} Wry and Winking
l-O Yawning
:-(0) Yelling
=8-0 Yikes!

...special thanks to Melisa C for passing these on.