Background information for events in the news.
Is this the most important value-added feature that the web provides to journalism?
Writing good and comprehensive background articles takes time. For more general topics you can usually find background articles at Wikipedia. The Economist also has "Backgrounder" sections and Country Briefings
If you have no time, quotes from other sources are a good way to begin creating a "Backgrounder". That's what I see some people doing at Wikipedia, like this article on Web Mashups (see the quotes section). Wikipedia on Quotes