Unfollowr – who unfollowed me
Unfollowr command center
See who unfollows you on twitter for free.
What is it? Unfollowr is the twitter service that helps you to track people that stopped following you. No more guessing “who unfollowed me today?” — you’ll know that for sure with @unfollowr.
You will receive emails with list of unfollowers (including ex-friends). All you need to start is authorize it to find your unfollowers.