Probably the best rail for a DIY slider, I believe this would be the same as a Glidetrack, is the Linear Guide rail from Igus. Normally used for Robotics, these precision machined aluminum rails use Dry bearings to slide. No greasy bearings. A.K.A. ZaZa slider, you can find more information here http://www.dvxuser.com/V6/showthread.php?t=145701
After reading a few threads and checking out the ZaZa slider group over at Vimeo.com, I decided to build my own. This post is really late because I had already ordered this item about half a year ago, but finally decided to finish it with a Fluid Head. It pretty much just sat waiting for this last piece. It's a work in progress, i'll probably change from one Tripod to 2 (1 each side) for more stability. I'll use Quick Release plates on each end to break it down faster. Oh well, here's my first run.
[Update] After the popularity of this DIY Project, the company IGUS now sells the complete kit and some predrilled. Here's the link to grab possibly the cheapest high quality DSLR Video Camera slider: Igus DIY Slider Kits