Youcubed: The goal of this organization is to inspire, educate and empower teachers of mathematics, transforming the latest research on math learning into accessible and practical forms. It provides research based teaching methods, daily math tasks, videos, and ideas.
What Works Clearinghouse: The goal of this organization is to be a central and trusted source of scientific evidence on education programs, products, practices, and policies. Research is reviewed and the studies that meet rigorous standards are summarized. Teaching practice guides are provided.
Mashup Math: Grade specific math resources, with free lesson plans, worksheets, and activities.
Khan Academy: Provides instructional videos, practice exercises, and quizzes.
IXL: Grade specific and skill specific questions and teaching examples.
Knowledge on the Go: Provides instructional lessons, practice exercises, & homework help.
Intervention Central: Interventions, cited references, & other resources.
National Center on Intensive Intervention: Math Strategies geared toward teachers assisting students who struggle in math.
Motivate through supplementary videos and games
PBS Learning Media Mathematics For Kids: FREE standards-aligned videos, interactives, & lesson plans.
Cool Math for Kids: Arcade-like games.