This is from the "Wow, this is free?" department. Have you ever needed to edit an image with Photoshop, but you were on a computer without Photoshop? Your wait is over, as there's a solution for you. It's called Pixlr Editor. Not only is it free, it's web based, so there's no software to install. The toolbar is nearly identical to Photoshop.
And, if that's not enough, if you only need to do basic photo editing, they also have Pixlr Express. Can you say "Photoshop Lite-Lite?". Give it a try!
Oh by the way, it does require Flash 10, so if you are on an iPad, I guess you are out of luck.