You can put one of those new compact flourescent bulbs into a regular incandescent socket - TankGirl I think has a post about that here.
Problem with the CF
bulbs however, is that they are quite bulky, and may not fit inside the hood. Also, the only CF
I can find here in Canada are warm white, not the right spectrum for plants. Someone had posted in the DIY
forum that they actually found plant light CF
bulbs at Home Depot, but I havn't seen it yet.
A cheap way to get a flourescent hood (which is what I use) is to just get the tank, put a piece of glass on top if you wish, and just mount some shop lights from the ceiling or an overhanging shelf.
Recently I checked out a high end lfs
in town, and all their set ups have glass tops & external lights (well, they use expensive light for the reefs, not shop lights!)