SculptGL

SculptGL is a web sculpting application, powered by WebGL and JavaScript.

SculptGL is a free 3D sculpting CAD (Computer Assisted Design) program created by Stephane Ginier, a University of Montréal exchange student. It lets users sculpt 3D designs, apply symmetry, import/export these files in 3D printable formats, and automatically share them on portfolio sites like Sketchfab.

Link: http://stephaneginier.com/sculptgl/