Interactivate is a collection of free math and science resources, including assessments, lessons, discussions, and activities.
Resources are aligned to NCTM standards and grade levels 3-5, 6-8, and 9-12. The activities are interactive and there is also a dictionary of science and math terms for students. The activities are well designed and fun and educational.
This is a great resource for educators to use as part of their lessons in class, for students to use as review or self study or to include as part of an online course.