Chuy-- rapidleds.com has some pretty nice packages and that's where everyone seems to go. They only have Cree LEDs. They also sell the drivers, voltage thingies, heat sinks, fans etc. In essence, it's a one stop shop to get all your led build going.
The other site that I am interested in is stevesleds.com. They have complete packages for sale: LEDs, optics, drivers, wire, solder, etc. it's complete and rather good price. The downside is the LEDs themselves, they don't use Cree. I dont know what brand they use because there is another led that rivals CREE's output for less money. I wonder if this is the one they use. And no steffen it's not Chinese. Well, I take that back, everything is made in China.
Theres another website that sells everything and will post it when I find it. Also, go to the main forum RC page and go to the diy link. You will find massive amounts of information and how to build a led setup. Thats where i am at constantly since i am going to build a led fixture. Good luck. Hope this helps.