“LibraryThing is an online service to help people catalog their books easily. You can access your catalog from anywhere—even on your mobile phone. Because everyone catalogs together, LibraryThing also connects people with the same books, comes up with suggestions for what to read next, and so forth.”
I like LibraryThing. I like it a lot. You catalog your library and it compares it to other libraries. Reviews, tags, 200 books for free. $10 for unlimited. $25 for an unlimited lifetime. The T I will try to do a widget out of it to the sidebar to show what I’m reading.