Check out this tiny house/playhouse that was built by the Habitat For Humanity crew in Fort Jackson, Mississippi! I love the front array of windows, the interior colors (mostly), and the micro second floor. The horizontally laid tongue and groove walls look great as well.
If you really take a look at this, especially from the outside, its got the makings of a GREAT looking tiny house or cabin for adults, never mind kids. Sure you'd have to tweak some dimensions, add a little bathroom, and some better second floor access (I'd prefer that at least), but its pretty much all there!
This house was ultimately raffled off as a fundraiser- talk about one lucky kid!
Again, I'm working on a coffee table-style book on kids forts, getaways, tiny houses, treehouses, and clubhouses (and their possibly design influence and ties to regular housing). If you have a project or have taken photographs of one that you'd like immortalized in a book, send 'em over to kidcedar at gmail dot com- I'd love to see/consider them. Hi-res/300 dpi+ photos only please. Perhaps we could feature them on this blog, or www.fortaday.com too.