Extreme wheelchair athlete Aaron Fotheringham recently landed the world's first wheelchair double backflip at a skate park in Pennsylvania on August 26, 2010.
Fotheringham is a pioneer in what he has coined "hardcore sitting" (a sport with tricks adapted from skateboarding and BMX). Fotheringham is known to be the first person to perform a wheelchair backflip (at age 14), and now, 4 years later, a double backflip. Amazing stuff.
Here is a great short about this group of pioneering "hardcore sitters" produced by Explore.