Step by step tree-houses
Cabin built for $500 with re-purposed windows in the mountains of West Virginia (with probably very little energy efficiency, but hey, it's pretty).
50 Kids Treehouse Designs. I think this is the winner for the new house :)
cool treehouse ideas
How to Build a Swing Set for the Playhouse!
Children play house adventure like the swing, slide and climbing wall
A frames are cool. And of course you need the bucket! ;O) 50 Kids Treehouse Designs