Every winter over the last few years, Mike Sandlin has designed and built a new glider design. They are simple, inexpensive, ultralight sailplanes, similar in performance to a hang glider, but they have 3 axis controls and a seat. They use unsexy materials; like weelbarrow tires, sailboat rigging, and irrigation pipe, but the designer seems to be quite happy with the results.

The Bug2 and Bug4 are biplane designs, and came first. Then the Goat, which is a monoplane, and has a little better performance. The Hillhopper was his 4th design, another biplane of even simpler construction (but you get the impression he doesn't like it as much as the others...). And lastly, the Goat2, which is very similar to the original Goat, except it's cable braced.

The designs are completely open source, you could download them and start building tomorrow. Pretty cool!