CK-12 Foundation
Ck 12: Earth Science: Geologic Time Scale Study Guide
Take a quick look at Earth's geologic time scale.
University of Colorado
University of Colorado: Ph Et Interactive Simulations: Area Builder
Create shapes using colorful blocks, and explore the relationship between perimeter and area. CCSS.Math.Content.3.MD.C.7.a Find the area of a rectangle with whole-number side lengths by tiling it
Other
Tone Savvy: E Music Theory
This site provides good online learning games and exercises for music theory. It also has a lot of options for teachers if they choose to subscribe.