Hi bamboozle
So sorry that you are depressed, it's a terrible state to be in. I've saw a really interesting lecture on depression the other day, maybe it would be interesting to you.
YouTube - Stanford's Sapolsky On Depression in U.S. (Full Lecture)
Also, an article in the NYT recently.
Depression’s Upside - NYTimes.com
I know that does not answer your original question. I don't know specifically of any online communities for depression for atheists, but there are quite a few vibrant skeptic/atheist communities out there, maybe posting in one of those would lead you in the right direction. The one I'm thinking of specifically is Skepchick, a great website of skeptic women.