[eschwartz]

The first post of the jailbreak thread (now this one) has all the details needed in the Installation spoiler. USBNetwork is a separate hack, you might want it, or you might not.

Note that calibre can manage the books on your device without any need of jailbreaking, both moving books to calibre (the send-to-device toolbar button) and adding books from the Kindle (either Add books ==> navigate to your Kindle's drive letter ad select books from the documents folder, OR click the Device toolbar icon, select books, right-click and select "Add books to library".)
Although jailbreaking opens the gate to other useful things -- like collections management from calibre, screensavers, USBNetwork for remote shell access, etc.