cool Treehouse/Playhouse by http://www.top-100-homedecorpictures.us/home-improvement/treehouseplayhouse/
Instead of a treehouse, build a DIY tree fort. Kids love multiple entrances and exits!
Cubby house! More
The Study House by Studio 30 Architects
Wow i like this!
20 Creative Ways to Repurpose Old Tires, http://hative.com/creative-ways-to-repurpose-old-tires/,
Log stairs on the side of the garage. Build in a slope next to stairs and you have an easy bike push path.:
Steps, this is brilliant!