Google is touting their Image Search as being an easy way to find images that are licensed as Creative Commons. This will allow you to legally use images in your blog or other purposes, that you find using Image Search. On their blog Google states that:
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.
So give Image Search from Google a try and see what you think.