Google Summer of Code ist a program sponsored by Google that does enable students to work for Open Source projects. GIMP did participate in 2006 and 2008, the results are listed on our Summer of Code wiki page.
We intend to participate again this year, and are currently collecting possible projects at our GSoC 2009 ideas wiki page.
If you think that you might have a possible project, then please go to the IRC channel #gimp on irc.gimp.org and/or the gimp-developer mailing list and present it there. IRC is good for the quick "could this be a project at all" checks, the mailing list is good if you've already got some kind of plan and want to discuss it in detail.
If you would like to mentor any projects, please announce this on the gimp-developer list and/or IRC. And please do reply to any mails sent to you.