We love community contributors at Mozilla!
I personally work on Marketplace [1], the app store for open web apps [2]. Our properties run client-side apps (HTML/CSS/JavaScript) with a Python/Django API server. Many other options are available depending on your skills and interests:
- If you know C++, for instance, you can contribute to the core layers of Firefox, Firefox OS, and other Mozilla products.
- If you know JavaScript or HTML/CSS, you can contribute to the front-end of Firefox, or to Gaia, the application layer of Firefox OS.
- If you know Java, you can contribute to Firefox Mobile.
- If you know Python, you can contribute to our web services, including Firefox Sync or Persona.
- If you know Make, shell, Perl, or Python, you can contribute to our build system.
- If you know C, you can contribute to a number of low-level and third-party libraries that we use as part of the Mozilla codebase.
https://developer.mozilla.org/en-US/docs/Introduction
http://whatcanidoformozilla.org
Feel free to reach out if you're interested (email in profile), and I'd be happy to either help you find something or put you in touch with somebody who can.
[1] https://marketplace.firefox.com/
[2] https://developer.mozilla.org/en-US/Apps/Quickstart/Build/In...