I was reminded of this site by a post on Learning Today, a blog on educational software which has led me to many great resources.
It is possible to search all the resources on the site, one could search for Interactives in Mathematics for example.
A useful Interactive for teaching probability is Marble Mania which is from Science Netlinks, It is possible to narrow the search to resources from that provider. In fact is it possible to search by keyword, resource type, grade level, subject and partner.
The majority of Mathematics Interactives are from Illuminations, the search tool is useful for looking for resources for particular topics; see this selection on Polygons for example.
