Jim Marske has been working on flying wing sailplanes for quite a long time. He currently sells kits for two designs; the Monarch, and the Pioneer. The Monarch is smaller and simpler, almost hangglider simple, and the Pioneer is larger, modern and sleek. It looks a bit like a Messerschmidt 163, except with a lot more wing.

Both designs seem to be liked by their owners, and kits are currently available, which certainly make it a better bet than trying to find an old set of Woodstock or Duster plans. Lots of info is available on the above website.

Marske's designs owe quite a bit to Fauvel's plank wing sailplane -- a french design from the 50's. You can find rather expensive drawings of the Fauvel here.