Glowdoodle
I created Glowdoodle in 2008 as an accessible new way to let people paint with light. Unlike the typical light painting technique, using a camera to take a long exposure, Glowdoodle uses your webcam and lets you see your painting appear in real time. Glowdoodle also makes it easy to share your creation, and the site hosts thousands of glowdoodle paintings.
I wrote a blog post telling the story of the project and what I learned along the way, including fire, flowers, zombies, and Dwight from the Office, here.