In-browser collaborative 3D voxel editor / modelling program which can import images and 3D models as well as export designs for 3D Printing (for your own or direct to the Shapeways service):
CubeTeam is a multiplayer 3D painting and modeling program that lets you and your friends imagine worlds out of cubes and then print them in 3D. CubeTeam is free, runs in a web browser, and has powerful editing tools that let you create in a virtually limitless environment.
CubeTeam is for anyone who wants to build 3D worlds or models. Whether you want to experiment with 3D printing, or just build worlds with you friends, CubeTeam is the easiest way to get started.
Here is one of the tutorial videos on exporting your works:
You can sign up and start creating at CubeTeam at their website here
CubeTeam also have a Tumblr blog [teamcubeteam] here