Have you run across LibraryThing? It is a wonderful social networking site (I'm absolutely sure I thought I would never say that) which lets users catalog, categorize, and search through their own libraries and the libraries of others. In fact, rather than list the many different features here, I would encourage all book-lovers to surf over to LibraryThing.com and check it out. My library is listed under jlhilljr; a search box and link can be found and the link bar on the right side of this page.
If you love to read, but could never see the point of Facebook or MySpace -- I fall into both categories -- I strongly encourage you to check it out.