My Twitter is way too busy. I want to know who I can unfollow to reduce the highest amount of messages. The messages are so spread apart it's hard to tell. There are also retweets. Is there an app that will do this? Since the API is available, I suspect this has been done.
Noisy Neighbours will inspect your timeline and provide you with a graph detailing your followers by number of tweets.
You need to authorise the Web App to read your Twitter timeline before using it.
It appears that Noisy Neighbours no longer works an alternative is ManageFlitter
ManageFlitter will analyse your Twitter account and provide with details on:
This should be a good start to help you trim down who you follow.