We stumbled across this Twitter Client today that runs on Adobe Apollo runtime platform. It looks like it is worth a look, it has URL shortening built in too. It runs on both Mac and PC. We haven't used it yet so let others know what you think if you try it. .

http://www.tweet-r.com/

P.S. - We have a list of about 20 apps that are waiting to be added into the Twitter Forge. They will be posted over the next week here...