Do you have a bookcollection?
If so: Take a look at librarything.com: Its an online bookcatalog with some social software functions: When you add a new book, the system tells you who of the other users has this book, which I think is pretty interesting - especially where only 2 other people has the specific book.
But you can also put you collection on your blog - Take for example, a look at this link cloud:
Im danish, and two thirds of my book collection is danish. Some of the tags that I use to describe the content of the books doesnt show the danish letters right. - And others do - This is a very mystic error, that I do not understand, but plan to solve.
Its pretty fast to ad books: The page communicates with a lot of different library and commercial book databases, so that you 98 percent of the time just have to enter the title. Many of the popular books also have coverpictures, and those who doesnt - you can add yourselves.
It has my warmest recommendations: http://www.librarything.com