Lovely idea by Volkswagen in Stockholm, Sweden. They have created a site called Rolighetsteorin.se or “Theory of Fun” in English (To translate text just use http://translate.google.com). The site features several videos all dedicated to the idea that happiness is the easiest way to get people to change. The three videos that are up there so far show how to make people not FAIL when putting litter in a bin, How to get more people to take the stairs than the escalator, and a teaser video of how to make recycling more fun.
The Piano staircase resulted in a 66% increase in people taking the stairs than the escalator, and the fun noise making little bin resulted in about a 70% increase in litter in the bins ! Nice one VW.