If you are a great fan of Twitter and uses it often, then you must be trying out TweetParty. Tweetparty is a service based on Twitter API which lets you organize your twitter friends into parties and send direct messages to them.
With tweetparty, all people you are following are downloaded when you login. You can then create as many groups as you would like friends and select the friends you would like in each group creating the party. Then through twitter you can send a direct message to any group without any other set up.
To send a direct message to your groups, first you need to add Tweet party to your friend list. Once this is done, you can send a message your any group using the format- #groupname This a sample message. Here groupname is the name of your group and next to it is the message. This will send a direct message to all the friends in the group. You can add or remove friends to groups by drag and drop feature.