The Sunlight Foundation released a new "journalistic accountability" tool today, wryly named "Churnalism". It tells you if an author was "churning" out somebody else's material by checking journalistic text against a database of press releases. To the dismay of plagiarists and lazy reporters alike, it even checks against Wikipedia.
The site provides a few examples. Enter this story from CBS News, for instance, about a mother who found the chemical BPA was linked to her son’s thyroid problems, and churnalism will provide you this press release that that the CBS article sources, and highlights the portions of text that match between the articles.
The Sunlight Foundation's Kaitlin Devine suggested in her introduction that users scan articles after they've been out on the Internet for a while; breaking news might not turn up a match.