it depends alot on what you want to do dude. i like once a week. but when i had more time i was doing double splits.

chest in the AM. Tris abs and calves in the PM.
Back width in the AM. Thickness in PM
Quads in the AM. Hams, calves in the pm.

that kind of stuff. you've gotta think about what you specifically want. to gain - HARD once a week is nice.
you want to cut, do everything twice, 3 times a week. everything over 2 days, 6 on, 1 off (i burned out doing that though)

right now, i've got back, legs, chest, shoulders, arms. 5 on 2, off. i particularly like the order too, everything sort of flows nicely. if i decide i need to i can take a day off between legs and chest and move arms to saturday.

options. gotta have 'em.