Pixlr is another great software for simple photo editing. It also has an iPad and Android app that works almost exactly the same as the online version.

If you want to do advanced image editing or image creation you can find Pixlr Editor on the Pixlr site as well. This tutorial only focuses on the simpler Pixlr Express.

This tutorial (designed for teachers or students) shows the basics of modifying an image. You'll see how to:
Open an image from your computer
Crop it
Add text
Add effects/overlays
Save