In retrospect, this is totally obvious, but Shapeways now provides a way to produce your own rubber stamp from uploaded images. Here's how it works, as shown above:

The service permits you to upload an image with multiple stamp images up to a size of 9x13 cm for only USD$25. We think this service will be quite popular, particularly with children - and apparently Shapeways does too, since many of their promotional pictures involve children's stamps. The only improvement we can think of would be for them to provide an online photo manipulation service that cleans up the picture and directly integrates with the printing systems.

This is yet another simplification of 3D print technology enabling more people to get involved. Yay!

Via Shapeways