Here is a classroom to use for children three and older, contains reading stories, games, lessons and music. http://www.bigfunreadingroom.com
It would be nice to know how it downloads to your OLPC, and get your feedback.
You can also try http://www.montessorihome.com/readingcards/ where you will find for the children of the world the words of the world.
Then see a sampler of our stories etc at http://www.montessorihome.com/sampler.htm
You help is valued.