Campfire is a team communication tool. The tool is fully integrated into 37signals' Basecamp product with features including group chat, file sharing, live image previews and chat transcript archiving.
A killer feature on Campfire is that you can have pre-setup chat groups. For instance, you can have chat group set-up for your companies interns. You can see when the group lasted chatted and what they chatted about.
Pricing starts at free for four simultaneous chatters and works itself up in tiers depending on how many simultaneous chatters you want.