Worldreader is a non profit that gives Kindles to children in sub-Saharan Africa. They just completed a study analyzing the effects of the one-year pilot program in Ghana, and the results are promising. There were significant increases in reading skill, in time spent reading, and in the variety and number of books available to the children. The program proved to be cost effective when compared to the price of shipping books combined with the short shelf life of a paper book.
Check out the links I've provided. If you are interested in donating your e-book to this program, the Worldreader site has the specifics on how you (or your publisher) can get involved.
For the latest bestselling e-books for kids here in the states, check this week's updated list.