Today, Google announced new Search by Image, which allows you to find the provenance of any image by uploading it. It's a handy way to find attribution for a photo you found out there randomly on the wilds of the internet, or to find out new info on stuff in your photos.
The search allows you to either upload an image or stick in an image URL. So if you put in a painting that you don't know anything about, it'll give you the full rundown of what it is and who did it. Same with locations and animals. You can also get a Chrome plugin to let you search any image on the web by simply right-clicking it. Seems like it could be pretty handy, no?