Siavash Eliasi gleefully shared his set of 17 Mesa patches on the Mesa-dev list after seeing the easy projects to get started with open-source 3D Linux graphics driver development.
The project he took on was enabling ARB_map_buffer_alignment for all Mesa drivers. Only some small and fairly straightforward modifications were required for enabling this ARB extension inside Mesa. The new contributor then commented in our forums, "Thank you very much Michael for covering this on front page! Hopefully this will help main developers to focus on delivering key features and attracting more people. First project was fairly easy and it was mostly a matter of looking up function definitions and replacing them ;)"
The developer has been responding to feedback from the upstream Mesa developers and adjusting his patches already to work out issues. For more ways to get involved with Mesa driver development, see this forum thread.