Ask HN: Which open source project to contribute?

I have some time to spare (1h/day or 4-6 hours per week and want to contribute to some open source projects.

But I cant choose which.

I have strong background in c/c++/embedded linux, some crypto background and know a handful of protocols. lately i've made some little webpages (for private) with ruby/bash for server administration.

Any recommendations where to look?

Thanks!