Sugar is the new interface for the OLPC laptops. Rather than simply using Gnome or some established Linux front end, the folks at the OLPC decided to desgn their own interface incorporating tools to assit if the educational and social-computing goals of the project.
For example, Mesh View is a way of displaying the active laptops in the mesh network-- the peer to peer wireless network the units generate.
Friends View allows users to add and remove friends and invite them to participate in activities with a few clicks.
Other collaborative software will include the widespread use of Wikis.
If only the software we adults use permitted that kind of easy collaboration!