Tweetspinner is a web based application with a few little tricks inside. They do require their own login to get started, which can be different than your Twitter credentials. Note the little checkbox to skip adding yourself to their mailing list. You provide an email address and password to gain access to the interface.
You can add multiple Twitter accounts to their system, using oAuth for each. The catch is that there is different levels of capabilities depending on what service you choose. You come in as basic level, with some limits in capabilities.
I was totally unsware of this when I first entered the system. Costs are free/$15 month/$21 month to pro (no price listed). You can add more Twitter acocunts with each level as well as filters, pruning and more.
There is no way to delete your account either, which I found interesting. FOr some reason I decided not to move on due to these facts.