I've got the whole world in my hand

Book Search

Google Books goes mobile. A quick scroll through looks promising-- I found Flatland: A Romance of Many Dimensions by Edwin Abbott right off the bat in the Science & Math section. It's one of my favorites and well worth a read if you have a chance.

More important is what this could promise for developing countries.  If the world's store of literature becomes available for free to anyone with a cellphone it suddenly opens new options in rural areas with cell access but without textbooks.  Combine it with something like MIT's OpenCourseware initiative and you're really talking about making the best educational material (although not teachers) available for free anywhere in the world.