Teachers know best what they and their students need on the XO.
If you are a teacher using the XO with your classes (or wishing you were), what kind of activities would help your students learn? If you are a retired teacher, what sort of programs would you have liked to be able to use with your students?
If you can come up with some very specific ideas, there is probably someone out there who can write the code for a down-loadable activity to add to your XO!
Let's make a wish list....
I'll start with...Basic Algebra practice activities available in many languages.