I thought that I had heard of someone who had built treehouses and was renting them somewhere on the San Juan Islands but I cant seem to find any info about it any ideas?

There is one treehouse cottage available for rent.  Here are the particulars:

All Dream Cottages include four fully furnished properties at various “dream” locations, all on the sunny west side of Orcas Island.  All have fully equipped kitchens, private decks and breathtaking views. Watch the sea ebb and wane, explore your private beach, fish if you wish, sleep to the sound of water lapping below your bed, and be mesmerized by the forever views and gorgeous year round sunsets at …our Sea Dream Cottage, your incredibly comfortable beach cottage located at the water’s very edge; unwind and take a nap on the hammock at our Isle Dream Cottage, your own waterfront hideaway nestled on its own hillside overlooking the calm deep waters of Eastsound; see the most spectacular sunsets on Orcas Island and listen to the trees whisper secrets to the sea at our charming Tree House Suite designed just for two; and take the time to stop and smell the flowers, listen to the birds’ song and count the bunnies hopping about at our Day Dream Farm Cottage, your own nostalgic country cottage surrounded by acres of meadow and woods. All self contained, all very special, all a dream. . . our accommodations are available by the day (2 night minimum) or by the week.  Come for a romantic weekend getaway or come to reconnect with nature and loved ones, come to rest, relax, rejuvenate, and reflect.

The All dream cottages website is: http://www.alldreamcottages.com/ . Doesn't look like it is actually "in" a tree but it does look like it "feels" like your in a tree.

Wes