This is a wordpress plugin which connects to twitter and will serve you a live stream of tweets. You can set it up to follow certain people or track words related to your site. All you have to do is add a [twitfeed] short tag to any page or post you would like to have the feed show on.
This is not a normal plugin in the respect that it does require some background processes to be running. Please take a look at the README for more information.
You can download it here.