Oddly enough, I signed up to mentor but don't have enough experience with any of the listed languages to do so.

I decided this spring to come back to Clojure (which I used in 2008-11) because, while I prefer static typing (slightly, although it's 51/49 for most projects) the community is one of the best out there.

I think the O'Reilly reference is a great starting point, and after that there's the Joy of Clojure, which is covers some solid territory.

The community is very helpful, so that's one thing to keep in mind. Don't be afraid to ask questions in the way one might in some other language communities.

Yeah the the community is incredibly helpful, but sometimes I wish there was one person I could just unload all of my questions at once to get a tighter feedback loop going. I think in the end there probably isn't much I already couldn't find out on my own or with the help of others for free, but this process could be a lot more efficient if I had an actual mentor.

Where do you live? It's probably harder to find what you're looking for in some places than others.

Have you tried using it at work? That will speed you along a lot faster. People fetishize after-hours work in this industry, but the truth is that it's usually better if you can find a way to make your day-job synergize with what you want to do in the long term.

We're focusing on a few selected categories in the beginning. Clojure is certainly what we'd like to get to next!

I had the same experience, but my greatest area of expertise is in Haskell.

I think you should definitely have things like C, C++, and so on.