The 6600GT is also coming out for AGP, infact there are now 3 available, at this time they are all over 200$, but they should drop to about 200$ soon:
Albatron Currently out of stock (only seller I can find)
BFG currently out of stock (only seller I can find)
I would stay away from the XFX version, as I have heard that they arn't too wonderful. And like I said, these are just early signs of the AGP version of the 6600GT, as more are released, and as more places start stocking them, the prices will drop.
The best way to go otherwise for AGP would be with the 9800 Pro, but that card is now starting to show signs of age. If you are getting a PCI-E Board, then there are alot more options at that price.