My kind of tree house.
Make A Kids Obstacle Course | Obstacle
Structural Creativity Education
Let Kids Run Wild, Build Forts, and Pick Flowers. Nature Can Take It.
Pallet mud kitchen
Welly storage from Millwood Education
Scramble Nets for treehouses by Treehouse Life "...a world away from everyday"
House Plan Queen of Hearts - aboveallhouseplans.com - not at all passive solar, but a really cool floor plan nonetheless
Solar System Coloring Pages (lots of them) More
Printable Solar System coloring page. Free PDF download at http://coloringcafe.com/coloring-pages/solar-system/