This is so ridiculous, but looks freakin' awesome!
You can stay in real tree houses at the Out 'n' About Treehouse Treesort (get it? haha) in Takilma, Oregon. It's a pretty lengthy drive from Portland (5 hours), but looks like it would be seriously fun. While you're there you not only have the opportunity to live like a bird for a weekend, but you can also horseback ride, raft, take craft classes, swim and more! And the best part of all... They have a zip line!!!! Count me in.
(photos courtesy of thingsyoushoulddo.com & oregon.com)