Find Creative Commons Images using Google Image Search
Great new tool:
Today, we’re launching a feature on Image Search to help you find images that you can use for free, while respecting the wishes of artists and creators. This feature allows you to restrict your Image Search results to images that have been tagged with licenses like Creative Commons, making it easier to discover images from across the web that you can share, use and even modify. Your search will also include works that have been tagged with other licenses, like GNU Free Documentation license, or are in the public domain.
via Official Google Blog: Find Creative Commons images with Image Search.