I've noticed several different versions of the 6800 GS AGP showing up both on manufacturer sites and on retail sites so the card should be available quite soon. I'm somewhat disappointed that the specifications have been altered quite dramatically from the PCI-E version though. The AGP version of the 6800 GS is based on NV40, the same chip as the 6800 GT/Ultra. Unless there's a possibility of unlocking the extra pipelines, the 350MHz core clocke (compared to 425Mhz for PCI-E) will be significantly slower than its PCI-E counterpart. If the pipes unlock the card will be a bargain, otherwise the price will have to come down a little before I'd recommend it. To see what I mean, take a look at the comparison linked below.
6800GS PCI-E vs AGP