Since I've already seen a lot of people asking for one and there isn't (as far as I know) one already in existence, I thought I'd start a list of all the Kinja blogs. You can see it here. I'm obviously still adding to it, so if you know of one that isn't on there yet, let me know in the comments. Once blog creation slows down a bit, I might open it up for editing so that folks can add their own blogs.
And please, share this post wherever you think people might like to see it!
ETA: Thanks to xeos, we now also have directory.kinja.com, which includes (or will include) the welcome posts from all of the group kinjas.