When I realized that my N900 was about the same size and shape as a small digital camera, I went looking for digital camera cases that would fit. The one I wound up getting is the Lowepro Volta 20:

http://www.lowepro.com/about-us/news...a-pouch-series
http://www.amazon.com/Lowepro-Volta-.../dp/B0029EB3OC

Padded interior, has a belt loop and a thin internal pocket. I'm pretty happy with it. I was using it with one of those Amzer silicone + polycarbonate protectors for awhile, but as others have noted, this made the camera case a tighter fit, and eventually one of the plastic tabs holding the protector on the N900 broke. So now I just keep the bare N900 in the camera case and hope that it doesn't jump out of my hands when I have it out of the case!