I'm a fan of the Coralife CFLs. The 10W bulbs aren't of much use, but I've run two 20W over a 6 gallon, four 20W over a 13 gallon, and two 20W plus two 15W daylight and a 15W actinic over a 16 gallon.
I'll be putting two 20W over a 7 gallon 'fuge on my next tank, but the display will be large enough to warrant T5s.
FYI - Canadian Tire, Home Depot, etc, sell medium-base sockets for about $5 each. Adding a $5 electrical cord and figuring out a way to attach these to a DIY canopy is simple.
Here are some old pics, before I swapped out the spiral bulbs for more Coralife 50/50s:
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FERRARI 312B HISTORY