Tweetparty.com - Send Group Twitter Messages

Tweetparty is a Twitter application that lets users save some time and energy when communicating with groups of their Twitter friends. Whether you need to let your friends know there’s a party on Friday night, or you just want to check in and say hi to a select group of people, Tweetparty will let you mass message in seconds.

To use this app, first login with your Twitter username and password. Next, add Tweetparty as one of your friends on Twitter. From there, organize your friends into groups, or “parties.” As soon as the groups are created, you can send one mass message out to them using Twitter. You can create as many party groups as you want, and add as many Twitter pals to each one.