From Kovid Goyal:
Calibre is program to manage your e-book collection. It acts as an e-library and also allows for format conversion, news feeds to e-book conversion, as well as e-book reader sync features and an integrated e-book viewer. It features library management, format conversion (all major ebook formats), syncing to e-book reader devices, fetching news from the Web and converting it into ebook form, viewing many different e-book formats, and giving you access to your book collection over the internet using just a browser.
What's new in this version:
Version 0.8.41 has added a tweak to Preferences.