A Drupal Planet post pointed me towards Sumarize.com which makes easy work of searching Twitter. Though it still doesn't make Twitter a really useful tool in most cases it is rather fun to use it to search "follower whores". Now what is a follower whore? It is somebody who wants to crank up their followers so they make their updates "private" and then allow anybody who will "follow" them to see the updates. With the search engine you can't see their feeds but you can see the responses to them and get a pretty good idea what they're saying.
And you can use their tool for sentiment analysis. Though to be honest when I use it and then look at the resulting posts it's a really weak analysis with really tenuous scoring. But tenuous doesn't prevent it being fun.