Topsy - A search engine powered by tweets

"Topsy is a new kind of search engine, with a new way of looking at the Internet. Topsy doesn’t think the Internet is a collection of documents. Or even a web of documents. Topsy sees the Internet as a stream of conversations. Topsy treats people differently from the webpages they create and the things they say. And Topsy sees that people in every community are connected in a web of relationships, where each person influences other people to read, talk and think about things."

http://topsy.com/