Adywan,

I saw something on a project website some time ago which was basically a cheap way of achieving a tracking shot. Instead of a big set of tracks, you make a mini track and mini dolly, then mount it between two tripods. Don't know if that'll help with whatever you're planning. And never forget you can always move the set instead of the camera...

Also bear in mind that green screen isn't going to be easy to achieve without high-end camera equipment. As I found out to my cost, you really want to be capturing in 4:4:4 (i.e., pro equipment) for a good matte. DV was good enough for my purposes, and you might be alright if you're shooting in HD, because the subsampling will be compensated for by the increased number of pixels.