If you like science fiction, Baen Books sells in un-encrypted and open formats, including rich text, plain text, and others. You should try their site. They also give away quite a few books in the free library. They also have a "webscription" deal that gets you several books a month at a very low cost.
Other than that, you can get them from news groups, and quite a few other web sites. I like mainly scifi, so I'm addicted to the Baen site.