Use pictures rather than words to guide Google's search results.
By now, just about everyone is familiar with Google Image Search. Type in a phrase, hit the button and you're bombarded with images that may or may not be related to what you were looking for. But now Google has reversed the process with Images.Google.com, allowing users to submit an image and get a pile of pertinent web results.
The project was unveiled at Google's Inside Search event. The feature will be rolling out over the next few days. If you go there now and see a little camera icon in the search bar, it's already enabled for you.
In order to search, you can paste the images URL (if it's already on the web), upload it through the browser interface or just drag and drop the image from your desktop. There are also Chrome and Firefox extensions if you feel like you'll be using it a lot. Once the image is processed, you're bombarded with web results as well as related images.
I tried a couple of my own personal images and it pulled up many other images with a similar overall look in terms of color and brightness. Picking a more famous image will generate more robust results, though you'll likely get some stuff that's just wildly unrelated.
While it may not be quite as focused as sites like Tineye.com, which offers a similar service, it's cool to see image recognition making leaps forward. I can only expect Google will spend some serious time honing the formula to make it truly useful for hunting down image sources or even cracking down on sites using images without permission.