I'm a long term GSoC mentor and org admin. In my experience most free software projects are always happy to have new contributors. And if you ask, many will gladly hand hold you through the initial stages.

In fact, personally speaking, I would be more willing to do so outside of GSoC than within the confines of a Summer of Code program. Usually because it indicates a slightly greater level of interest, and more importantly we're not under a time pressure to get things done. It's more relaxed this way making the whole process more enjoyable.

Hit me up and I can introduce you to multiple projects within the GNU ecosystem that would love to have a new contributor.