New site announced that offers public domain ebooks for both Palm- and PocketPC-based PDAs. Not sure there's anything different compared to similar sites, except for the interface, but it's worth a look (any site offering mobile content is worth a look!). Files are in PalmDOC format for PalmOS, and Microsoft Reader for PocketPC:
They also offer a mobile version, but oddly enough it's intended for PocketPC because you can only download Microsoft Reader formats via their mobile link:
