I'm looking for mailing lists, web forums and other discussion sites. I hope to participate myself, so the sites must be more-or-less openly accessible. The topic that interests me is moral philosophy (ethics), but the sites needn't be specific to that topic, of course. The crucial thing is the quality of conversation. What is your short list of the better discussion sites?
We have a chat room, and we could even consider organizing group readings or discussions if that might be interesting to people. As noted in comments we can create rooms for particular themes or problems. Also mods can create "gallery" chats where only certain people can talk -- this might be helpful in terms of facilitating more structured interactions like debates.
http://philosophyforums.com is a well-trafficked site with an area devoted to ethics. Personally, I'm not a huge fan of the site, but it might be your best bet for an active, online philosophy discussion community.
You might also try http://philosophy.meetup.com and look into meeting up with local philosophers offline. I don't know where you're located, but here in Columbus we've used the meetup site to arrange a monthly philosophy discussion for nearly ten years now.