I'm also a mentor for Gentoo again this year, after taking a break last year.
You can find our list of potential ideas here: Google Summer of Code 2010 ideas for Gentoo
But don't limit yourself to them! Creative ideas can get you very far too :-)
I'll also be the infrastructure contact for the accepted SoC students, for any issues you have with the source code repositories (we'll be offering Git again), your shell accounts, and a sounding board on deploying your successful project (for those that hosting or larger resources).