I just finished making a tripod into a dolly for my video work, initial results are pretty good.

How I did it here for $40...
Tripod Dolly DIY using Casters (http://blip.tv/file/3310027)

Next project is a follow focus for $30, after that I have some plans on Glide Track and Camera Stabilization.

I like the idea, thanks!
Will go to a hardware store and check out if there are similar parts I can use.