80/20 is a great material for a linear track system.
Go to
http://www.8020.net and search for your local dealer. 80/20 is sold wholesale from the factory so you have to go through a middleman. Tell him about FIRST too, and maybe you'll wind up with a sponsorship or a discount.
The pieces you will need will be, obviously, two pieces of 80/20. One serving as a track, the other as a moving piece. Then you will need connecting slides. To make the moving piece, well, move, you will need to figure that one out on your own. Ways done in the past: pnuematics, bolt a moving chain, etc.