I've always loved shooting tennis. It's tougher than it looks. Well it's easy to get the player hitting the ball. The hard part is getting it all in focus.
I've taken these shots with the Sony A55 which has a real-time autofocus. It doesn't predict where the focus should be, but continues to focus in real-time even while you're taking the photo. The fact that it's 10-frames per second helps with getting the ball in the shot.
Now the hard part about shooting tennis is getting accreditation to the big tournaments.
You can see a video about this shoot here.