In my experience[1] the best way to get contributors is exactly the opposite, you have to leave the easy and cool parts for new people and do all the grunt work by yourself. Making a new feature is something fun that other contributors can try to do and learn a lot, while optimizing your website is something that mostly only saves you money (as contributors could do that virtually anywhere else and learn the same). See an example of what I mean: [2]

[1] http://github.com/franciscop/

[2] https://github.com/umbrellajs/umbrella/issues?utf8=%E2%9C%93...