Twellow – Twitter yellow pages
Twellow is a great new search tool and directory for discovering Twitter users that could fundamentally change the way people use the microblogging service.
Launched by the same people behind the tech news site WebProNews, Twellow has indexed more than 300,000 users and sorted them into categories like programming, marketing, graphic design, and dozens of others to help you find users who list those characteristics in their Twitter biographies. There are also sub-categories. RSS feeds are also offered for each category and sub-category.