backbone.io
This project is deprecated and will no longer be maintained. I've taken the best ideas from the project and incorporated them into a more versatile and well-designed library for syncing data via Socket.IO. You can find it here: https://github.com/scttnlsn/data.io
Note that data.io does not depend on Backbone (like backbone.io did) so if you're looking to integrate data.io with a Backbone project please refer to this example.
If you have any questions or run into issues migrating your code to use data.io, please open an issue in this project's tracker.