If Parkour is the art of running around town like a maniac, pretending to be a ninja, then doing that on a bike is Parkour-Plus -- actually it's just stunt bikes. That's marketing for ya.

There are so many amazing stunts in this video, I'm not even sure I could describe them, although the first two minutes are amazing. The best has to be towards the end where you see people looking over the edge of where they saw a bike drop, expecting to see a bright red blob.
(:flash http://www.youtube.com/v/Z19zFlPah-o&color1=0x234900&color2=0x4e9e00&hl=en&feature=player_embedded&fs=1 width=425 height=344 :)

This is the way to commute to work. Music by Band of Horses is damn fine too. Find more here, or just head over to the source at Danny MacAskill. Or go and buy a trial bike from Inspired and break your ass.