Google Scholar offers many scholarly open-access articles, which are freely available on the web. However, these are mixed between scholarly fee-based articles, which are available for purchase, and with non-scholarly articles.
Hosted by Library of Congress, the American Memory Project provides access to a number of collections about American history and culture. It uses historical images, sound recordings, and film recordings to document significant national events. Collections are put together by theme to form online exhibits. Most content is free of copyright restrictions.