The basic we know for a long time now: 3DS will show the 3d images without need of any special glasses, it will have gyroscope and accelerometer for move detection and will be similar with DS only much stronger when it comes to hardware.
The release in Japan is scheduled for 26.2. 2011 with the price range of 300 $ .
What is in the package?
With Nintendo 3ds we will get a recharge station and 2 GB SD memory card. What is interesting that when we buy a game on DSiWare shop we will be able to easy transfer that game to the other 3DS console without any problems (this thing is not possible on DS)...