I've used Campfire by 37Signals and thought it was pretty cool. A bit pricey for me though and I would only use it with friends so I want a free alternative. Found TalkerApp and they offer a do a free version but it only offers public chat rooms. Google Chat and Skype would've been great but they don't offer persistent chat rooms ( as far as I know)  and I would like the option to have the transcripts of conversations. 
Open-source Campfire alternative
chat
There's a list here:http://alternativeto.net/software/campfire/That might be useful.Echowaves might fit the bill (open source)Hope this helps.