Topsy

"Topsy, a search engine powered by tweets, is designed to mine the collective signal from the social web in real-time. To measure the relative importance of each search result, Topsy examines the links being cited, the description of these links and the influence of each person citing a link. Topsy augments traditional search engines by finding interesting and relevant information that people are talking about. If other people are discussing it, Topsy thinks you might find it interesting and relevant too"