"If you could commission a computer demonstration of any categorical idea, what would you ask for? Could such demonstrations have helped you, or your students, learn tricky ideas? And, would you be willing to share the visualisations and metaphors that you have devised to explain these ideas to yourself or others?" We've started a thread on this topic at the n-Category Cafe', http://golem.ph.utexas.edu/category/2009/04/graphical_category_theory_demo.h... . Anybody interested in using computers to demonstrate concepts from category theory, do please have a look there. I've just added an explanation of the techniques available for delivering demonstrations over the Web, and I mention one - the 3D modelling environment called Alice - that I think will eventually be brilliant for animating category theory, and many other topics besides. Jocelyn Paine http://www.j-paine.org http://www.spreadsheet-parts.org +44 (0)7768 534 091