On Moomin Light there is a post about the Frank Gehry designed Stata Center on MIT's campus. The Stata center is one of the most playful structures built, and has caused a minor uproar and a lawsuit because it has practical problems. See Moomin Light's post for more details and some photos.
When I read it, though, I thought of another playful structure, designed not by an architect, but by a painter - one of my favorites - Hundertwasser.
Here is the building. It is called the Hundertwasser House, and it's in Vienna. He also encouraged residents to be playful with decorating inside, with some beautiful results, like a sunflower mosaic in one of the stairwells, I believe (I can no longer find a photo of that image).
For more photos of Hundertwasser architecture see the following Flickr items:
A waste incinerator in Austria
A church, several different photos
A market building in Switzerland
A public loo in New Zealand - outside and inside and another view inside (oh no! not more urinals!)
And more photos of Hundertwasser House
Here is a Hundertwasser painting so you understand the inspiration behind the buildings. There are further samplings of Hundertwasser's paintings at this link (also in my sidebar).
I bought a lovely book of Hundertwasser paintings which I still have wrapped, still in the bag from a Nashville, TN bookstore near Vanderbilt. Like an unopened REM album (also stashed in my art table), it's a horded treasure I will open when I either really need it, or when I'm in the kind of expansive mood where the new art will blow me miles up like a hawk on thermals, to soar and scream with joy and pleasure at the flight.