Khan Academy - A non-profit educational organization created in 2006 by educator Salman Khan to provide "a free, world-class education for anyone, anywhere." The organization produces micro lectures in the form of YouTube videos. In addition to micro lectures, the organization's website features practice exercises and tools for educators. All resources are available for free to anyone around the world.
National Library of Virtual Manipulatives - The National Library of Virtual Manipulatives (NLVM) is an NSF supported project that began in 1999 to develop 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). The project includes dissemination and extensive internal and external evaluation.