Sculptfab!

Sculptris is an elegant, powerful and yet easy to use 3D sculpting software, allowing the artist in you to simply focus on creating amazing 3D artwork. Gone are the technical and often tedious constraints typically associated with digital art.

SculptGL is a small sculpting application powered by JavaScript and webGL.

meshmixer is an experimental 3D modeling tool for making 3D mashups without too much hassle.

SharpConstruct is an OpenGL graphics application that supports real-time sculpting of polygon meshes. The process is similar to painting on a canvas in a traditional 2D image program, but with an added dimension. Depth is simply brushed onto the model, offering an easy way to create highly detailed meshes.

Dilay - a 3D sculpting application.