Update: there's an orientation session on 9/13/15 if you're interested in helping
I built a small, fun Rails app called ignitespeak to manage speakers and proposals for Ignite Baltimore. I've long thought that it would be a great project for beginners to work on, because it's well-tested, it gets regular use, and it's open source.
I have an ambition to make the app more useful and available to all Ignite organizations around the world. If you're looking for a way to break into Rails development, and would like to get my personal attention, advice, or mentoring on your commits and pull requests, please contribute! I created a number of Github issues for some possible projects.
If you're really serious about gaining more Ruby/Rails skills, I'd even be willing to do some pair programming with you, either remotely or at an open source hack night.