Bookbaby, a website that offers print on demand, self-publishing and editing services, has a dozen free guides for authors. These cover a variety of things, such as epublishing, using Twitter, blogging and promoting your book, and are available as PDF downloads here :
http://www.bookbaby.com/free-publishing-guides
(note that they can all be downloaded in one go, by using the link at the bottom of the page)