On a regular basis:
DM: DnD3e
Player: DnD2e, WFRP, Ars Magica
Other games I've played (but now on hold or campaign finished):
DM: X-files(home brew system based on L5R)
Player: 7th Sea, Deadlands, CoC(classic),
Some day...? (characters made but not played yet)
Player: Hiboria, STNG, Top Secret
Furthermore I have books on (but never played or DM'ed)
Pendragon, L5R, Hackmaster, Sovereign Stone, Star Wars, Alternity, Dark Matter, Milleniums End, Harnmaster/world
(these are either used as background material, inspiration, to be played some day (when I'm retired) or simply because it are nice books, I love books)