Have a look at the bosch rexroth aluminum framing.
The 20-series profile is pretty cheap. Even Mark from Mr. Saltwater tank uses it to mount the Radions over his new tank.
The design is only limited by your imagination.
Skip to 6:00min to see his light rail.
http://www.youtube.com/watch?v=BLK4t-Qg_EY
This is the Bosch catalog:
https://dl.dropboxusercontent.com/u/....com/bosch.pdf