I have come to this question or an issue perhaps in finding an apt open source project to contribute to.. As for beginners, it gets even tough since everything is relatively new and in a complete blank where to start and how to start.. I had these problems while starting out (which is I am doing now).. I find hard time searching for projects that uses my skill and knowledge level for the benefit of community but still couldn't..That's Why I created this repo in Github called OpenSourceForBeginners which basically is an index of open source projects that are required contribution and defined skills required for contribution.. Link is below.. As for as traditional Open Sources, I have started it and it will get in shape only after.. but I don't know what to do next.. Need all your help here..
https://github.com/avinoth/OpenSourceForBeginners