Heya, I use a 95 watt full spectrum envirolite CFL, and I must say, I've had fabulous results. My light sits mere inches off my plants and I usually have to move it up every two days. Potroast is right though, mine cost me bout' 100$CAD with taxes. Though it doesn't screw into a regular socket. The lamp's self-ballasted, but i had to build a conversion socket. I attached a mogul socket to an extension cord with a couple of electrical connectors. It plugs straight into my power bar and works great, i recommend it to anyone.
Hope it helps, Sgt. Stoner