XP Math is a great math resource for any age group. The site contains math games by subject area, a math careers exploration area, forums and homework help, and a math resources section that contains eBooks, worksheets, videos, and teacher resources.
Teachers can use this site in their classroom, or just let their students know about the site as a help resource. The site is free, easy to use and navigate, and is well designed. The games and resources are fun and well-designed. Some of the free videos are from the Standard Deviants School series.
The site is a must-use for any math teacher or student.