Project Gutenberg is the brainchild of Michael Hart. Starting in 1971 he, with an ever increasing crowd of volunteers, has been digitizing texts into simple .txt files and making them available at this site. They focus on out-of-copyright books and their range of books is staggering. Children's books are only a portion of what is available here. I use them for finding especially obscure exploration and travel texts but there is something for everyone.