[dgunay]

Most of my open source contributions have come from necessity, either for work or for a side project. I would say you should look at tools and libraries that you use frequently, especially if there is something small about them that you think could be improved.

You can also look at it from a more negative ideological perspective: are there any pieces of software you wish would just go away? Support their biggest competitor by using and contributing to it.

I don't typically start by looking for a project and then finding ways to contribute. I've had limited success doing that (usually by searching on GitHub by language and issue tags), but none of my contributions that I'd consider truly valuable have come about that way.