A new and interesting tool is available free in beta to actually search the Internet for a particular image, TinEye.com, image search engine. You can actually enter an image's URL or the actual image file and TinEye will tell you where it's also displayed on the Internet. It doesn't search by file name but the ACTUAL image! Very kewl!
This service is free and can provide you with additional information such as what browsers, screen resolutions, and keywords your website visitors are using.
This 'Linkblog' contains all of the important sites linked to in our articles.