[K-12] Virtual Manipulatives for Interactive Mathematics

From Utah State U,

A library of uniquely interactive, web-based virtual manipulatives or concept tutorials, mostly in the form of Java applets, for mathematics instruction (K-12 emphasis)... Manipulatives [are] physical objects that help students visualize relationships and applications... A national library from which teachers may freely draw to enrich their mathematics classrooms. The materials will also be of importance for the mathematical training of both in-service and pre-service elementary teachers.