There are some forums that you could use as well that have member created backing tracks (such as this one). That is if you didn't want to take the time to create your own. Some of them are quite elaborate.
This is a particularly good one you could try:
http://www.guitars101.com/vb/forumindex.php
You will need to register with the forum in order to download...but that is free.
Most of the ones I've seen on this site have, at minimum, a drum track. Also, I'm sure there are other forums out there as well.
Tom C