Open Atrium is an intranet in a box that has group spaces to allow different teams to have their own conversations. It comes with six features - a blog, a wiki, a calendar, a to do list, a shoutbox, and a dashboard to manage it all.

Blog: A classic blog for each group that has commenting, file attachments on both the post and comments, and granular notifications.

Calendar: A calendar that lets you quickly add events, suck in iCal and other calendar feeds, and support single or multi-day events.

Group Dashboard: Mini widgets give you a snapshot of all the activity happening across your groups. Think iGoogle, in that you can turn on what you want, turn off what you don't, and arrange it all however you'd like.

Documents: A simple online handbook that lets you collaborate on documents, store and compare revisions, attach files, and once you're done print out the final copy.

Shoutbox: Kind of like a private twitter, the shoutbox lets you share short messages, links, and information with just the people in your group.

Case Tracker: A full ticketing system that lets you assign to do's and create unlimited projects within each of your groups. The case tracker also lets you classify the to do, give it a priority, and manage its status.