If you want to do sequences, you really need 7 frames per second at least. The cheapest camera I know of with that fast a drive is Minolta's Dimage 7i, which is about $1000. You can
get away with a slower drive though, on smaller jumps or slower rails - I took these photos with a 2.5fps Canon S200:
You can't really go wrong with higher-end Canon, Nikon, Minolta or Fuji.