Twitter is evolving from simple chatter to themed content distribution. The jump was made with the roll out of a new feature - Twitter lists. News media organizations have been fairly fast to utilize this feature. Most notably, the New York Times dedicates a screen on thier site to lists [hat tip Zee]:
The power of Twitter is in the people you follow. Let @nytimes lead you to the best of Twitter: follow our lists or build your own. Suggestions? twitterlists@nytimes.com
The Huffington Post seems pretty well on top of the content it covers with its lists. Other news businesses have started their own lists as well. Among them:
CNN - not as comprehensive as I would have thought, but they have many Twitter streams