Try this superb site.
Feature articles rotate, usually to commemorate the anniversaries of important historical events.
There's also a weekly quiz and dozens of categories of links. Points off for the many advertisements and links trapped in frames, but those aren't that interesting and thus aren't hard to ignore. The government has been publishing reams of documents that nobody reads for years. With the Internet, especially this site, you can find those documents and use them. This site has links to all of the federal government departments and agencies.