Just want to mention this because I never see it in lists like these, yet everyone I've recommended it to has been blown away.
Talkerapp: http://talkerapp.com/ - It's a free Web chat system (with a paid level for extra logging and file transfers). I believe it's open source too. I use it for some of my online courses and haven't had another Web chat system come close (although stylistically it's a bit like Campfire).
Talkerapp: http://talkerapp.com/ - It's a free Web chat system (with a paid level for extra logging and file transfers). I believe it's open source too. I use it for some of my online courses and haven't had another Web chat system come close (although stylistically it's a bit like Campfire).