I also frequent Atheist Discussions and Atheist Nexus. The latter has a chat room that used to be quite active, with 8-12 participants posting there each evening. Interest started to fall off a few years ago, however, and I'm lucky to find even one other member at a time there every couple of days.
"The world is my country; all of humanity are my brethren; and to do good deeds is my religion." (Thomas Paine)