Utwitmore is a twitter based service that will help you to make long tweets. You can login to utwitmore via your existing twitter user name and password.
To post tweets simply login to utwitmore and type your message in “post message” box and finally click “Post to Twitter” button then the tweet will post on your tweet page. Tweets will cut into small tweets and post it 140 word tweets. You can add URL to message and Upload image to twitpic also.