Hey Goliath,
Last I heard, the Corps isn't taking any ground slots right now. They say they're all booked up.
As for other jobs, there are plenty. Infantry, Artillery, Motor T, Law, Supply, Special Ops just to name a few. The Marines are a smaller force, but they still have to have most of the other positions that all the larger forces have (there are just fewer of them).
I'm sure that someone with prior service in the Corps would be able to shed some light on the subject. Check out www.usmc.mil as good place to start.
-Matt