LibraryThing.com
LibraryThing a website for all the book lovers out there. It’s got an interesting way of connecting people. Specifically, you can upload your library titles, and it will compare and introduce you to others with similar tastes in literature. I highly recommend it if you’re looking for a good online community about your favorite books.
For the web developers out there, it’s got an API that allows you to pull information about your library. I’ll be writing up a plugin soon to do just such a thing on this site. Click here if you want to get started on one yourself.