AT&T just published the “Coming Soon” page for their Nokia Lumia 900. You can enter your email address so you can get notified when the device will become available for purchase. A good guess would be the week of April 9th.
The Nokia Lumia 900 has a 4.3″ ClearBlack display, 8MP camera with Carl Zeiss optics, 1.4GHz Snapdragon processor, and of course, the Windows Phone OS. If you need a refresher, here’s a hands-on video.