That is a pedal-powered roller coaster from Japan, the Skycycle at the Washuzan Highland Park in Okayama to be precise. I first saw it written about on the Everyman Triathlon blog, as a way to actually combine the very disparate concepts of "endurance training" and "fun". The post there has more information and pictures, as does this one from Geekologie, from March of 2007. Finally, there is this page, linked to in the Geekoligie article, which has a lot of details on the Skycycle.
I don't know about you, but I would love something like that to play on. I mean, I live in the SF Bay Area, one of the most dedicated liberal/green enclaves going, and we don't have a human powered roller coaster? What are you greenies thinking?