Twellow is a directory of public Twitter accounts, with hundreds of categories and search features to help you find people who matter to you.
Keep track of conversations that mention you, your products, your company, anything, with hourly updates! You can even keep track of who's tweeting your website or blog, even if they use a shortened URL (like bit.ly or tinyurl.com).
A unique tool created by Edelman - measures an individual's importance on Twitter.
The basic idea of this site is that a brand exists entirely in people's heads. Therefore, a brand is whatever they say it is.
1.7 million + tags and counting.