Math Virtual/Digital Manipulatives:
http://nlvm.usu.edu/en/nav/category_g_3_t_1.html
http://www.glencoe.com/sites/common_assets/mathematics/ebook_assets/vmf/VMF-Interface.html
http://www.mathplayground.com/math_manipulatives.html
http://www.symbaloo.com/mix/onlinemathmanipulatives