Then look at Github or here, find projects you find cool, and contribute to them and write about that. If you don't know what you can contribute to, ask - most open source projects can always need more contributors.
The beauty of github is that you don't have to ask. It removes that particular (and possibly socially awkward/difficult) barrier of entry, for new people. You simply fork a project that you want to make a change to, make the change, and then send the pull request (it's literally just a button in github you click).
If they don't accept the change, don't take it personally.
