Jared Abrams at Cinema5D posted links to a couple of videos showing a very impressive quadrocopter being used as an aerial platform for an HDSLR. Makes for some impressive shots.
Cinema5D: Perspective Aerials Helicopter HDSLR Rig.
If you're interested in building your own quadrocopter, you can find information about a system from one company at Quadrocopter LLC, and there are more examples of aerial shots posted on Vimeo by user FLV-Leif, including this one: Random Okto. The test shot with a Sony HDR-SR10 is good too.
There's also MikroKopter.
If you want to go a little simpler than these multi-rotor systems, you could go to an RC helicopter: DIY Photography: Photographer Rigs A Canon 7D To an RC Helicopter (Kickass Video + Short Interview)
But having attempted to pilot an RC helicopter, I'm going to stay away from these things, and try something more like this: Kite Aerial Photography: Rig and Camera