theworldofdreams.com

This is arguably at least partailly a commercial site so not really sure if it's cool to post or not ...

Anyway just came across these guys.

Seems to be a good sized collection of older books that are downloadable in various formats, some of which seem to be for specific kinds of PDA's or something, you might need to try a couple to see what's best for you.

I love free books on the internet. Here is one of the best free-book projects available: http://www.promo.net/pg/
Project Gutenberg has 1000s of copyright-free books that have been put into electronic format and work with most PCs and PDAs.