AGEIA PhysX cards are now available in stores from Asus and BFG at Newegg, Bestbuy, Tiger Direct and Circuit City. It looks like the BFG’s will be hitting the streets before the Asus cards as I was unable to find a link to an Asus PhysX card. You can read the press release here
If you want to jump in at the deep end before the card is fully supported, be my guest and lemmie know how it goes!