With the growing significance of social media like Facebook, Twitter, blogs etc. several search engines have been developed to search these social conversations. Samepoint, for example, allows you to search across millions of conversations occuring on blogs and social media sites like Facebook, MySpace, Twitter, LinkedIn, YouTube, and lots more to find out what people are saying about a particular brand, company or topic.
Other similar search engines include SocialMention, Yauba and BoardReader, some of which offer RSS feeds and realtime 'buzz' about your chosen topic.