You can probably mail a maintainer or a developer for hints of a project you'd be interested in. Or better you can send a question to the project's mailing list

You can probably mail a maintainer or a developer for hints of a project you'd be interested in. Or better you can send a question to the project's mailing list. People there often are very helpful. I've done that. It worked. (I haven't tried contributing to any Google-managed projects though.)