MediaChance.com has some great free digital photo programs. They are very specialized tools, but they work great.

IrFanview is a great program for viewing images of almost any format. It reads most camera RAW files as well as proprietary and universal image formats.

Paint.NET is a free program that is designed to compete with Photoshop and CorelDraw. It works well, but is not the most intuitive.

Gimp is another free opensource program (free to use and change). It works well, but it is a little tough to install for a beginner. You must install the runtime program before you install the actual program. See linked page for details.

Let's not forget Picasa. This wonderful program lets you sort, backup and view your digital photo collection easily.