[daleharvey]

There are several ways to get started and it depends a lot on your motivations and are of interest. However the main piece of advice is to jump in, dont be worried about upsetting someone system, some OS projects arent setup well for contribution and they will become easy to spot, but for the ones that are, doing something 'wrong' is a great way for a maintainer to come along and help introduce you to how to do it 'right'.

http://openhatch.org works a lot on making initial contributions easier, if you are interested in express then you dont need to work on the core framework, write a plugin and open source it, contributing is by far easier when you have a real need to do so, maybe someone will use your plugin and find a problem they want to fix, maybe you will use someones project and want to fix something.