If you’re researching a topic related to the federal government, chances are the Government Accountability Office has already looked into the issue and published a detailed report about it.
This is a nice touch by a federal agency that for years has offered e-mail updates to subscribers, who can be notified about topics that interest them. I also noticed today that the GAO’s home page has an RSS feed.
The main resource I use is the GAO’s search page, which offers a rich source of material. You can do keyword searches on GAO reports going back to 1980.