Making learning Fun. Algodoo.
http://www.algodoo.com/wiki/Home
Algodoo is a fantastic software that provides a unique learning experience for kids and adults is derive from Phun a software we describe here a while back.
See prior post on Phun at
http://blog.isallaboutmath.com/2008/06/09/livios-mathematical-creation-with-phun/
