http://digitizor.com/2011/06/15/google-search-by-image/
http://www.google.com/insidesearch/searchbyimage.html
Here is a video that Google has released introducing Search by Image:
http://youtu.be/t99BfDnBZcI
Suppose you have an image you want to search about. There are three ways for you to use Search by Image to search for the image:
* You can upload the image.
* You can also drag and drop the image into the search box.
* If the image is online, you can paste the URL of the image into the search box.
* You can also use extensions for Chrome and Firefox that Google will release.
After the image has been analyzed by the servers at Google, Google will attempt to identify the image and bring up search results related to it. The technology used for Search by Image is similar to that used by Google Goggles for smartphones.
The service is not live yet and Google will roll out the feature in the coming few days. You will know that Search by Image has been activated for you when you see a camera icon at the right of the search box.