Instead of those arbitrary picks, how about looking at Google Summer of Code? Those projects have conveniently listed what things they want help on and already

Instead of those arbitrary picks, how about looking at Google Summer of Code? Those projects have conveniently listed what things they want help on and already have allocated mentors to lead those projects. While you might not be a student, if you really want to help out, I bet most of those projects would welcome additional involvement and the mentors would be willing to talk with you if you are serious about helping.