Grade 4 curriculum material on Curriki. There are three units: (1) Number, Number Sense and Operations (2) Measurement (3) Patterns, Functions and Algebra
This site contains many lessons that are very practacal. Activities regarding questions we may have wondered about might be found here. For example, how to measure the circumference of the earth. The lessons are described in text form, however, so if you are looking for an interactive lesson that is ready to go then this is not the place to look. On the other hand, there are a lot of really good ideas that are worth exploring.