National Library of Virtual Manipulatives. Gizmos! Online simulations that power inquiry and understanding. Math Manipulatives. Math Manipulatives contains three pages of resources: About Virtual Manipulatives What is a virtual manipulative?
In What are Virtual Manipulatives? , Patricia Moyer, Johnna Bolyard, and Mark Spikell (2002) defined a virtual manipulative as "an interactive, Web-based visual representation of a dynamic object that presents opportunities for constructing mathematical knowledge" (p. 373).