Croquet is a peer to peer collaborative 3D world. Avatars within the Croquet world can interact with objects, and the lower level messages are replicated within the peer group. He demonstrated this by manipulating some windows in the world, along with more complex objects. He also demonstrated stepping through a window ... a portal ... into a moon/mars scape. Moving through these portals allows the avatars to enter into alternative worlds. They both went through a portal into a "water world" and immediately transformed into fish. As they swam around they came across a "text editor" white board thing ... and edited the text on it.
Ok ... he just opened a paint panel and drew a fish, colored it, and then inflated the 2D fish as he dropped it into the world. Now both of them were able to manipulate and move the new fish around. He entered another portal and showed a interactive spreadsheet, with the inherent ability to graph the values contained in the chart. He also demonstrated using windows as filters to show a filtered view of anything behind it. He was able to move it around showing the wire-frame models beneath the textures mapped onto objects.
All of this is written in Smalltalk, and uses Squeak ... completely cross-platform to Windows, Mac, and Linux. He indicated that they will have a Python, Ruby, and other language support soon.
Hat tip James Governor