This time I sent just one proposal, choosing NetBSD as the mentoring organization. The project is entitled Automated testing framework and is mentored by Martin Husemann. This framework is something I've had in mind for a long time already; in fact, I also applied for this in SoC 2006 and attempted to develop this project as my undergraduate thesis.
For more details on what the project is about, check out these notes.
At last, take a look at the full list of accepted projects for NetBSD. It is rather short unfortunately, but they all look very promising. It is a pity ext3 support is not in them, but getting ZFS instead will be good too.
Edit (April 19th): Fixed a link.