I sometimes find that I am following many Twitter users who actually do not tweet very often. In fact, there are some who might tweet just once a month or so. This defeats the whole purpose of following them onTwitter. UnTweeps is a free online service that shows your all your friends that do not tweet frequently, and lets you mass unfollow them.
UnTweeps uses OAuth authentication for accessing your Twitter account. You can enter number of days, and then UnTweeps will show you all your friends who have not tweeted in those many days. Then, you can unfollow them if you want.
UnTweeps also lets you Whitelist some Twitter friends. For example, there might be some Twitter friends that you want to follow even if they do not tweet enough. You can add those friends to Whitelist, and UnTweeps will not show them in its result.
UnTweeps is an easy way to keep your Twitter user list clean. If you suspect you have fake Twitter followers, you can use Fakefollowers to identify them.