I recently made a really simple Backbone.js extension (https://github.com/napoleond/localModel) that reduces load times and the number of HTTP requests an app needs to make by caching data in localStorage. It was built as part of a closed-source project, so I can't use that as an example and I haven't had time to port the standard Backbone example (http://documentcloud.github.com/backbone/examples/todos/inde...) to a version which makes use of my project. What we need is the server half of the example app. It will only take a few hours to build, but I am unlikely to get to it for at least a week so if you do it first I will accept your pull request and thank you at the top of the README. (The client side of the example app is exactly the same as the standard example, but with the modified Backbone.sync pulled out.)
It won't make you famous, but it would be a very easy and useful contribution to an open source project that you could use on a resume or something.