In this form of searching, you upload an image, sketch or 3D object, and you get results based on where the image comes from, where else the image is placed and if (and where) there are similar images on the net.

Image Searchers:

retrievr – search by sketch / search by image
Sauce Nao

3D Model Searchers:

Prinecton 3d model search engine (also for sketches)
an article about the Purdue sketch / 3D searcher
Im2GPS Estimates geographic information from a single image

keywords: pictures, photos