Behold is a search engine that is designed to help you find the best Creative Commons licensed images for your blog, slideshow, or video project. Behold searches the catalog of more than one million Creative Commons licensed images on Flickr. What makes Behold different from just searching by using the license filter on Flickr itself is that Behold searches not just by image tag but also by the quality of the content of the images. When it works correctly if you used Behold to search for images of "buildings in New York City" you would not only be searching the tags people assigned to their images, but you would also be searching the actual content of the images.
Applications for Education
When students create multimedia projects in my classroom, I require them to use either Creative Commons or Public Domain images if they don't create their own images. I do this to teach and reinforce the point that they cannot just grab and re-use images without regard for Copyright. Behold could help my students find quality images that meet my Creative Commons requirement.