Check out the latest (beta) version of Tweetdeck. It has a really cool integration with Facebook that pulls in Facebook updates exactly like a twitter stream. Looks like Facebook is about an inch away from replacing twitter updates. I set it up to show: All Friends; Replies; DMs; Searches + Facebook updates!
The second thing I think is really interesting (depending of course on how you set it up) is Twitterfall. I got that one, courtesy of David Henderson. Anyone that wants to track a trend, or a real-time view on any topic via Twitter needs to set this up. You can even hone in on specific geographic locations. In this case its giving me a real-time stream of people tweeting about Lijit and Lijit-related stuff. A must for anyone in marketing or needing to pay attention to a market or trend.