TwitterStats - Measure tweets, better understand how your tweets perform
ilo - Premium Twitter analytics
Tweetastic - Better Twitter analytics, scheduling and more
Followerwonk - Followerwonk by Moz is a Twitter analytics tool to help companies better understand their Twitter followers.
Accountanalysis - A tool to evaluate Twitter accounts
Social Viewer - Find out your follower's most popular locations, interests, frequent used hashtags and twitter handles and more.