Kovid Goyal has just posted the weekly update to calibre.
Today’s update adds a number of bug fixes, tweaks, and a duplicate feature has been removed. But the important change this week is that calibre now supports direct downloads from Project Gutenberg. On a related note, the Open Library has been removed because its contents duplicated the eBooks accessible through the Internet Archive. Both PG and IA eBooks can be found under the “Get Books” option.
Calibre is the leading eBook and eReader management tool, and that’s not the usual marketing nonsense. It supports conversion from and to a wide variety of eBook formats. It will also assist you in organizing your eBook library and transferring your eBooks to your eReader (almost all are supported).