Hey blindsquirrel,
the PS3 camera is definitely the best bang for the buck. Cheap and works well. I use a unibrain fire-i with the infared lens coating. It is more money by far, but i dont have to take anything apart

(and it is firewire, and you can chain them together)
Also, it looks like Sandor has just beaten me to the punch

I was going to ask if you already had a tracker setup, or a table built, and if not, then, as Sandor suggested: hit the nuigroup:
nuicode.com/projects/wiki-book/files
Cheers!
-Ben