Using the browser to twitter is just too clunky for frequent/constant use. I first looked for an iGoogle applet for my iGoogle homepage, there were quite a few but I couldn't configure any to work. Then I tried a few desktop applications, which were not consistently functional, finally a fellow twitterer (is that right?) suggested Twhirl. I installed Twhirl which required an Adobe Aero to be installed first.
I can highly recommend Twhirl its compact, has nice little popups that notify of new messages and parks away in the tray when minimised.