I find volleyball one of the most difficult sports to shoot. Lots of bodies in a very small area with half of the athletes on the court behind a net--tough to find focus and capture peak action.
If the facility allows for it, I prefer to shoot from an elevated angle. I find this helps me focus on players a little bit and helps clean up the backgrounds, which are mostly the floor and not rafters or people in the stands. Of course, shooting from such an elevated position almost requires longer (and fast) glass such as a 300/f2.8 or 400/f2.8 lens.
Here are a few samples. I believe these were all shot with a Sigma 120-300 lens on a Canon 1dMk2n body.