Picasa3 Image Viewer – Since I use Picasa3 to organize all of my digital photos, the latest release of Picasa now incorporates a nice snappy (quick) image viewer which was not available in Picasa2. Highly recommend.
XNview – Over the past year I’ve been trying them all. My criteria for viewing images is simple. The program needs to open fast, zoom up and down with my mouse wheel, and do simple editing. XNview is a very close second to Picasa3 and I still recommend it.