I recently found out an interesting Web 2.0 book site for book lovers. It is called LibraryThing and lets you create your personal books catalog online, and also share it with your friends, tag and comment the books, see who else has the same books, get suggestions by readers with your same reading pattern, and even provide services to authors.
They've activated my author account at http://www.librarything.com/author/cantumarco
I've added only a few books to my personal library (with only a handful of the hundreds of books I own) and there is also a profile page. Finally, I've added a widget with random books (not only technical ones, as you can see) in the sidebar of the blog web site. Time permitting, will add more books and filter those in the widgets by "tech" tag...