Topsy is a real time search engine for the social web. What this means is that it indexed results based on "social data" that is found on the web through: tweets, diggs, hits, etc. Some nice features of this site is the ability to share results via twitter, being able to embed to a Topsy buzz feed into your site, and much much more.
I recommend checking out Topsy by clicking here!!
Thanks to Richard Byrne for the tip!!