BG: big grin
BRB: be right back
BRT: be right there
BTA: but then again
BTW: by the way
C: see?
CID: crying in disgrace
CNP: continued [in my] next post
CP: chat post
CU: see you
CUL: see you later
CYA: see you (later)
CYO: see you online
DBAU: doing business as usual
DD, DH, DS, DW: dear daughter, dear husband, dear son, dear wife (often used on boards where you discuss personal things, but wish to keep private the names of your loved ones)
EIP: editing in progress
FTW: for the win or f*** the world
FUD: fear, uncertainty, and doubt
FWIW: for what it's worth
FYI: for your information
G2G or GTG: got to go
G: grin
GA: go ahead
GAL: get a life
GF: girlfriend
GFN: gone for now
GFY: go f*** yourself/good for you
GG: gotta go/good game
GJ: good job
GL: good luck
GMBO: giggling my butt off
GMTA: great minds think alike
GSOH: good sense of humor
GTFO: get the f*** out
GTG or G2G: got to go or get together
GYPO: get your pants off
H2G: have to go