I could definitely see a newsletter happening if someone would volunteer to ping me and any other developer, say, every week or every other week to ask what I was up to, and then compile the list and post it somewhere.
I could see it happening in other ways, too, but I think that would be a good way to get it off the ground.
The "here's how you get involved" doc is important, and I encourage you and others to start compiling that as well. I have some thoughts, but I think it's best if a recent newcomer takes the time to write the "what I wish I'd found in a document when I started" document.
Mentor: Also yes.
There are many great ideas, we just need to pick some and make them happen.