For public domain books, if you want custom PDF files for the Sony Reader with advanced typesetting support, TOC etc... you can try our PDF output on Feedbooks:
http://www.feedbooks.com/discover
We already support .epub files, a new standard for e-books that'll be supported on the Sony PRS-505 as soon as Adobe DE is available for it (stylesheet support is sweet).
There's also hundreds of LRF files available on this forum, created with BookDesigner.