Nokia announced the N810 at the Web 2.0 Summit. Engadget (1st link) and Information Week (2nd link) both have coverage on the announcment (nothing on the Nokiausa.com site yet).
The first thing you notice about the N810 is that it has a physical slide-out QWERTY keyboard (see the photo in the Engadget article) unlike its touchscreen only devices that preceded it. At $479 it should make for an interesting race between the N810 and the Asustek Eee PC. The N810 doesn’t have has much storage as the top-end Eee (although you can insert an SD flash card for more storage), but it is smaller and lighter. The $1000+ UMPCs based on Microsoft Windows need to get into the $500 price range if they intend to compete in the nano-scale mobile market.