Really excited to find out about Topmod. It's a complex open source surface modeler that lets you quickly produce really neat knots, forms, and mind-bending geometries such at the one below. That was about five minutes or so worth of work. This is one of the things I love about Open Source. Tools that really don't have any viable commercial application beyond being fun to play with doing something cool can flourish and survive. While I've seen folk do similar work in Rhino, this tool seems way easier (if not as precise with it's non-NURBS basis). I see us using this in the (very near) future to make some complex light fixtures. Or at least some complex sugar structures! Check out the gallery for some very impressive models, and then fire up those 3D printers!