Open Source Apps
If you don't want to spend any money but still need to do some image editing, there are a few alternatives. GIMP is a very powerful image editing application that is very similiar to Photoshop - you can actually do almost all of the basic stuff and quite a lot of advanced techniques, all with an application that is FREE.
Another very cool application for browsing and tagging images is IrfanView. Both these applications are worth checking out.