In your post you mentionned that a goo way to start working with open-source project it to look for smaller scale projects to contribute on github. If been working hard to make it easier for people to find interesting/smaller projects on github by creating the /r/coolgithubprojects and the
http://coolgithubprojects.com/ website lately. It's not perfect but anyone who's looking to contribute and find interesting will (I hope) find these tool useful. They're not perfect yet but we'are working hard to making open source project sharing as easy as possible!.
My 2 cents.