Interested to work in startup web project and want to opensource

I am programming since last 6 year in lot of old age technology. In my spare time learning stuff like Rails, some time Django and some time other stuff. From long time I am interested to contribute a open source project. But I am not getting any motivation to contribute in a library or already big framework likes Rails.

I know I can program and build the things. Though I am not expert in Rails, but as there are too much for me to learn. So I don't think my self to contribute anything there. Also after reading tons of article about how to contribute on open source I realize that, only after I encounter some bug it is better to fix it and send pull request. As I am working in some corporate technology in day job. And not getting proper motivation to kick off a side project. Though I did few of them, but not as successful. And after few day I don't get much motivation either.

Now I am interested to work with some one who passionate to build something. And open source it. So we can collaborate on git hub. I am open to technology such as Ruby or Python or JavaScript (CoffeeScript :) ). We can brain storm on ideas, I have few. I am sure you have few.. We will pick some one and start coding and keep moving the wheel.