Are the forum abbv's in the wiki? I haven't looked, but have noticed they're thicker here than other places I frequent.
GH = GeekHack, a self-referential TLA (CTLA? 'constrained three-letter acronym' ...)
MD = massdrop, although this is noticeably less common than
DT = Deskthority.net (oooh! the competition!)
TKL / WKL = Tenkeyless / win(dows)keyless
GB = group-buy (agreeing to buy a bunch of one thing to get a volume discount)
IC = interest check (should anybody bother trying to organize a GB?)