Photoshop is king. There is no doubt!
If you are into heavy image editing, please get Photoshop. Amazon.com carries the latest full version (CS4) for less than $600! Word of warning: Amazon changes its pricing a lot. One day it will be below $600 and the next below $700. Please keep checking! – Link to Photoshop CS4 on Amazon.com.
If you need an image editing software for basic work like cropping, resizing, fixing red eyes, etc, you have a lot of good choices:
Photoshop Elements – $79.99
GIMP - FREE
Paint.NET – FREE
Picasa - FREE
They are listed in order to having more to less features. Picasa is a photo album organizer with lots of editing tools. Psst! It is the easiest tool to fix red eyes! 