Old school:
i.e. = id est (= "that is")
e.g. = exempla gratia (= "for example")
etc. (not "ect," etc.) = et cetera (= "and so on")
vs. = versus (= "against," duh)
a.m. = ante meridian (= "before noon")
p.m. = post meridian (= "after noon")
m.o. = modus operandi (= "mode of operation")
n.b. = nota bene (= "note well")
cf. = confer (= "compare")
nasa = national aeronautics and space administration
viz. = videlicet (= "namely")
et al. = et alia (= "and others," and why is that abbreviated?)
ncc. = non circum copulare (= "no screwing around")
c. = circa (= "around")
Q.E.D.
P.S. (oh yeah, post scriptum...)