drum tracks for jamming are free and bountiful on the internet..and tools for building your own beats....but none of it will ever replace the musical spontaneity of a real drummer.
Go to Mp3.com and search for "Drum Beats" or "Drums." They have a few people that made drum tracks from real drums. There's some that are complete songs and there's some that are a short beat with single hits of each drum and cymbal at the end.
It's a great tool!