"The leading blog search engine, Technorati.com indexes millions of blog posts in real time and surfaces them in seconds. The site has become the definitive source for the top stories, opinions, photos and videos emerging across news, entertainment, technology, lifestyle, sports, politics and business. Technorati.com tracks not only the authority and influence of blogs, but also the most comprehensive and current index of who and what is most popular in the Blogosphere."
TinEye is a reverse image search engine. You can submit an image to TinEye to find out where it came from, how it is being used, if modified versions of the image exist, or to find higher resolution versions. TinEye uses image identification technology rather than keywords, metadata or watermarks.