I came across this thread when I began looking for a way to use a standard USB cable to charge my iPad. I had two reasons for wanting to do this. 1) I wanted to leave my iPad cable where I use it at home, so I didn't need to pack it up and unpack it when I travel. 2) I wanted to cut down on cable bulk in my luggage.
Like sark666, I had hopes for the camera connector. When I found that it wasn't suitable, I continued searching until I found this:
http://www.podgizmo.com/products/125...c-adapter.aspx
Amazon also sells a retractable sync cable for a little higher price.
With either, you still need a USB power source, but those are pretty easy to come by.