BookKeeper is a project mainly written in RUBY and JAVASCRIPT, it's free.
Basically, a card-catalog system
This project was started as an exercise in order to learn web application development with Ruby on Rails. Fuctionality will grow over time, and contributors are welcome, however the first few revisions are mostly going to be based on my personal need to keep track of a fairly extensive personal library, with stashes of books both at home and in my office.
Future versions will contain a more generic data model which will be of more use to the general public, including public and academic libraries.