On my 10G nano I have a standard Incandescent canopy/fixture combo; around $25. I added 2 screw-in, self ballasted 20W PC bulbs; about $20 each. You can get bulbs that will fit anywhere from 9W to 28W and Coralife has a 50/50 bulb that will fit also. This is a cheap solution, you may still have the canopy if your tank was originally a kit. Many LFS in your area (Kevin's, Paul's) carry these parts.
Pros: Cheap. No extra ballasts or cords. Cheap. Super easy to put together, no DIY canopy etc. Cheap. Did I say cheap?
Cons: No seperate light timing. No "placing" light over certain parts of the tank (but face it, it's only 20" by 10")
