According to the latest data from Hitwise, Twitter sends most of its traffic to Google, Facebook, TwitPic, and MySpace. Overall, Twitter sends about 1 in 5 users to social networks and another 1 in 5 to entertainment sites like Twitpic, YouTube, or Flickr. Even though some people think that Twitter is just a 'poor man's email system,' Twitter's clickstream profile is very different from that of most email services.Twitter is a great place for folks to share links to resources. Makes sense to get gov links on Twitter.
There are a number of interesting results in Hitwise's study. Among others, Hitwise notes that a higher share of downstream clicks from Twitter.com go to blogs and personal websites than from search sites, social networks, or email services. A larger number of Twitter users are also being sent to news and media sites, which points towards Twitter's growing role as a medium for sharing and breaking news stories. --More from Read Write Web.
An easy way to use Twitter is to automatically send your agency RSS blog or newsroom feed to Twitter by Twitterfeed. Not the sexiest use of Twitter, but one that doesn't have much lift and can help broadcast information. See, for example, the Department of Labor twitter account.