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ATI's cards:

Radeon 9600 series
Radeon 9700 series
Radeon 9800 series
Radeon X800 series
Radeon X1900 series

nVidia's cards:
As far as I can tell, all of nVidia's current cards, Mac or not, support 2 monitors. It's hard to tell by looking at their site which ones are AGP though.
 
I know awhile ago I bought the Geforce 5500 AGP, and that had dual DVI inputs. I would assume if a card that old had two, the newer cards would as well.

Don't quote me on that though, just an assumption.
 
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