Hi
From the top of my head
ARP - arpeggiated
VO - voice (usually vocal pads, in Gladiator the vocoder sounds are also prefixed VO)
PA - pads
SY - synth sounds
LD - leads
BR - brass sounds
TG - trancegate
BA - bass sounds
AT / ATM - atmospheric sounds
FX - effects
DR - drum based sounds (single hits, drum sequences)
GT - guitar
OR - organs
PI - piano
EP - electric piano
FL -flutes
NA - natural sounds (usually emulations of traditional instruments)
ST - string sounds (think violins, orchestral string sounds)
Should be most of them I think, several are used somewhat ambiguous at times due to overlap between them, i.e., ST and GT
There's not really a golden rule when it comes to category prefixes so used terms may differ from designer to designer.
edit: and as George noted the postfixes are the designer's initials Hope that helps.
-Bastiaan-