Couple of Twitter lists compiled recently:
Iain Dale has the top 20-ish political twitterers who also have a blog. Congrats to Matt Wardman for getting in amongst them.
Church Mouse has the 'top 10 twittering bishops and clergy', based on a twitter grading site, updating a previous list based on number of tweets. Peter Ould has a list based on the number of followers, which updates automatically.
If you're not on any of these, rejoice! The last shall be first, and the first shall be last.