Great piece on the pulp comic characters that appear in the new series of Alan Moore's
League of Extraordinary Gentlemen Tom Strong (thanks, Zed) funnybook. These characters, like The Terror and The Fighting Yank, are in the public domain because their original publishers didn't register (or renew, it's unclear) their copyright, which means that they've been granted a new lease on life in Tom Strong. The article segues into a very good discussion of the public domain. This was just Slashdotted, so it might be a little slow, but it's worth the wait.