I really like how the site is broken down into segments of engage, explore, explain, elaborate, and evaluate for the students. This helps them to understand and dive a bit deeper into the content.
The interactive glossary on the side is great! It gives the students a definition, animation, video, and image of the word. This reaches so many learners.
There is also a PowerPoint that would help even non-science teachers feel comfortable with teaching the concept.
Here's a screenshot from the North Carolina 7th grade Weather and Climate Unit:

If you haven't looked at Discovery Education recently, you should do it this summer! They are doing an awesome job!