It's not as silly as it looks from the title
I could quite easily set up a dedicated Jabber server using OpenFire... that will allow us to have chat-rooms dedicated to a specific topic and to save all the text server-side automatically.
But I don't know if it's useful enough to be worth the pain of switching to another chat.
We could also use an IRC channell somewhere (or even set up an IRC server... but I know very little about that). I don't know about saving the channels' logs however, also if you're behind a company firewall IRC isn't easy to access.