Stumbled across this cool visualisation project by Petra Isenberg at Calgary University. Collaborative tree comparison uses a tabletop system to enable two (or more) people to interact when comparing (in this case) phylogenies. I want one!
The system is described in "Interactive Tree Comparison for Co-located Collaborative Information Visualization" (doi:10.1109/TVCG.2007.70568), a PDF of which is available from her web site (which also has a great video entitled "how co-located collaborative data analysis should not take place").