XMCA
The "Mind, Culture & Activity" listserve is a highly unusual online community that discusses everything from bunny cognition and short shoes to the meaning of life, time, and language. Ostensibly, the group is focused around Vygotskyian activity theory, but of course, as the name suggests, this theory is permeable across lot of areas. Some of the most interesting minds I've never met speak to one another here (where am I anyway ???) with varying degrees of success. It's always interesting.
If you wish to join xmca, you'll have to talk to the resident gremlins who inhabit the xmca server. Usually, if you follow the instructions, you get on the list. However, the techno-gremlins who live in the machines there often respond unpredictably. Sometimes, they unsubscribe people at random, other times you get messages saying that they can't unsubscribe you because you don't exist -unsettling to say the least. Such intimidating assertions rarely, if ever, come from the human inhabitants of xmca.
If you have an interest in minds, cultures, or the things they do, xmca will interest you. If not, you could always try the Dada Engine or something a little lighter.
Soon, we'll find out about the Big Brownout, a function of the xmca gremlins, which followed closely on the heels of the increasingly famous "Hodges Incident" which, of course, cannot be alluded to here because of its extremely sensitive nature.