Barbara Butler, who has some great treehouses and play structures that have appeared in several treehouse books, has a great website: http://www.barbarabutler.com/. She offers both pre designed wooden play houses and 2-story play sets, as well as site-specific, redwood play structures and children’s treehouses that come in all shapes and sizes. Take a look at her website, and buy the book “Treehouses — the House that Jack Built”, which features my treehouse and also one of Barbara’s structures.