Go to manybooks.net! It's a great collection of ebooks of any shape and size. They seem to be mostly culled from the Gutenberg Project, that venerable archive of public domain texts.

The great thing about manybooks is that you can download the files in a dozen or so different formats, so it will look good and be easy to read on your Palm device, Blackberry, iPod, etc. And it's all free. They do, of course, accept donations for this very worthy cause.