Here are more nice assignments from BBC.
I particularly liked this one
A good way to summarize what we had been doing with the rock cycle.
Same format, each lesson has an interactive flash video where the students have work through a introduction exploring the subject. The assignments seem a good level for middle school or to refresh knowledge for high school students.
Each section is followed by a short quiz to show their knowledge.
This page includes, assignments on chemistry and biology as well as the earth science.