Khan Academy

From Education Week:

On March 22, at the annual conference of Computer Using Educators, Khan Academy announced new resources, including thousands of free, interactive online math exercises for grades K-12, each of which has been pegged to the new standards and organized into “missions” meant to cover an entire grade level of content. As almost all states move to implement the new standards, thousands of educators are searching for relevant instructional resources, which has spurred competition among traditional educational publishers, other for-profit vendors and Open Education Resource providers, such as non-profits, universities, and government agencies.