I filed a bug here that would be a great way for someone to jump into contributing to swift-corelibs-foundation:
The basic idea is that we could really use a way to run our Swift test suite against the system (OS X) Foundation. This will help everyone to verify that the behavior of the library we are building is the same as OS X. If it’s not, then we know we have a bug to resolve in some way.
Let me know if you have any questions,