Saw this app when I was "Stumble Upon" had a look and thought it was a very good image viewer. It supports RAW images direct from your camera so therefore you do not need PhotoShop CS only a camera which it supports. I have not downloaded as yet because I normally use an HP bit of softtware to do that or PS itself as my browser.

Click on the link below:
http://www.faststone.org/FSViewerDetail.htm