We were just discussing GSoC a bit, and another idea occurred to me:

• Survey existing language implementations and how they're solving similar problems like POSIX, code generation/compilation, parsing, and so on, and work with project leads to pull out common solutions into reusable APIs.

This would be a huge help to all such language projects, since we all really want to work together but we're generally swamped with fixes and whatnot for our own projects. It would even be possible to narrow the focus a bit, such as to take on POSIX and use Tom Enebo's current library in JRuby as a base to start building out complete JVM POSIX support for all languages. If you're interested in helping JVM languages succeed, this would be a great way to help them all at once.