So what's so interesting about a gear made out of wood? Take a closeer look: it's elliptical!
Woodworker and artist Steven Garrison made helical (and helical-elliptical) gears using conventional woodworking techniques. Though such gears probably have no real world purpose, they are cool to look at in action: http://www.stevengarrison.com/id5.html (with embedded YouTube clips - don't miss the second one from the top) - Thanks Rob!
Also check out Steven's helix forms that fit together.