Nintendo announced today that the 3DS will launch on September 29 and could possibly ship out before 2011.
As for the other details, there wasn't much except the 3DS will have a much larger screen, an analog control pad and a gyroscope for tilt-sensitive game play. It will also be able to access the internet through the built in Wi-Fi connection.
As usual, Nintendo is pretty tight lipped on all the details. I am actually surprised they said as much as they did regarding the 3DS.