An unlocked Nokia Lumia 900 is now available for purchase on eBay from All_Electronic_Store, which is also selling the Lumia 800 (unlocked) in cyan and magenta varieties. The estimation for delivery is March 9-15th, which would tie in with the exclusivity closing up for AT&T.
The price tag is $895, but more than worth it should you be after a 4G Windows Phone sporting a front facing camera and quality hardware. You never know with listings such as this so proceed at your own risk. You can check out the auction and make your purchase by following the source link to the item listing.
Source: eBay (available in black and cyan); thanks, djohns505, for the tip!