Here’s a list of the top 50 slebs using the microblogging platform, courtesy of The Times Online. The league is purely based on follower numbers.
Lots of people are tracking the who’s who of the twitterati nowadays as more celebs start using the platform as a way to interact with their fans.
I am freelance 
I’d like to see a list of the Top 50 companies using Twitter. Twitter is not just a great tool for individuals to create a following but for Businesses to interact with customers at a much more stripped down level.