PBase

Here is a list of several free for home/personal use photo editing programs. There are many free programs available, a Google search returns a lot of hits. These have been favorably mentioned by users on other photography sites. The only one I have experience with is Irfanview, I don't about the others.

Some of these include RAW converters, and the features vary significantly between them. As an example, Gimp is pretty well known. The author of Gimp Shop rewrote the user interface to make it more like Photoshop.

IrfanView
http://www.irfanview.com/

Gimp
http://www.gimp.org/windows/

Gimp Shop
http://plasticbugs.com/?page_id=294

Serif Photo Plus 6
http://www.freeserifsoftware.com/

FastStone
http://www.faststone.org/FSViewerDetail.htm

Picasa
http://picasa.google.com/

Paint.net
http://www.getpaint.net/index2.html

VCW VicMan's Photo Editor
http://www.vicman.net/vcwphoto/index.htm

And one of my favorites is:
Neat Image noise reduction http://www.neatimage.com
They have a free version that limits size of photos you can use it with, but it's great for web shots.