You follow a number of people on twitter and actually don’t know who of them are very active, regular and who are totally inactive and not tweeted since quite some time. There is no use of having a big number of people whom you follow when you are not getting any updates from them on twitter.

Untweeps is a service that lets you know which of the people you follow are inactive since long time, and asks you if you want to unfollow any of them. It is a service which lists the twitter users who might not have updated since 7 days, 1 months, 3 months etc. depending on your choice and then shows you the entire list.

You can select all and unfollow them together and if you still want to follow few inactive people from the list, you can deselect them too.
Also, the tool shows you the list of users whom you have blocked on twitter.

Check out the tool at Untweeps!