Other thoughts for the summer of code...
* I don't know if such a thing exists already: use SWIG to generate the FFI for C libraries.
* Languages running on Gambit: e.g. implement Ruby or Javascript compiling to Gambit, at least simple demonstrations of those languages for the summer. A neat demo would be subsets of Ruby, Javascript, and Scheme compiling into their own shared-nothing processes (much like Termite), and allowing them to pass constant Scheme data or maybe JSON structures back and forth to each other.
(And then use that XMPP client I suggested earlier to pass these things to other Gambit processes on other machines.)