LibraryThing allows you to put your book titles online. You can enter 200 titles for free. For an unlimited amount of books, it is $10 for a year and $25 lifetime membership. Joining is extremely simple...no first name, last name, secret question, email address, repeat email address, jumping through hoops. Adding books to your collection is as easy as joining. Just type in the title or author. A selection will come up and you click a title. After joining and adding some books, you are able to see who shares the same books. There is an active forum for discussing books and anything else you want to get off your chest.
If you want to share your collection in your blog sidebar, a widget is offered. You can configure it as you like.
Here is my little widget.