http://www.squidsoup.org/doodle/

DOODLE is a work-in-progress exploring the possibilities of intuitive and direct drawing in 3D virtual space. Built to use a Flock of Birds (from Ascension Technologies), we have also made a (limited) demo using a conventional mouse. The 3D version allows for creation of drawn 3D shapes (spirals, swirls, faces, handwriting through to more complex objects). It was built as the basis of a drawn sound or drawn flora project (both in progress). Try the 2D version below (Shockwave needed)