Freeware for learning about math, physics, and engineering. Math quiz has the Space Invaders type look and feel where the math problems fall down the screen. You can also take a look at the virtual generator which shows you how electricity is made.
Biogas and How to Make a DIY Anaerobic Digester (Video) - " Biogas and anaerobic digestion made number one in HowStuffWorks' list of wacky alternative energy, and poop-to-energy biogas projects have proven popular on Discovery News too.
DIY Solar Lamp: Make your own Eco-Friendly Sun Jar. This is simply a way of taking an existing solar lamp ( garden stake style) and gluing it (solar panel skyward) inside a sealable jar. Soak up sun outside in the day, use indoors at night!