The best results people talk about have been with floodlight style lamps. Either fluorescent or halogen the internal reflector makes a big difference focusing the light into the fuge. A regular spiral fluorescent at the right colour temp (Philips Daylight are cheap) works too but I got way better growth the the floodlight.
Here's an article:
http://www.melevsreef.com/fuge_bulb.html
I use a 75w Philips Natural Daylight halogen from HD and it works very well, pretty good colour on it, I'm guessing around 4500K. It was only about 10 bucks but it throws a lot of heat so the fluorescent is probably a better choice.
You can order the bulb that melev uses from here:
http://www.lightbulbsdirect.com/page...ctors/1P381951
I'm changing up some of my FW tanks soon so I've been thinking about getting some and I think someone else was talking about them recently as well.