History Today Unfortunately, it's not all archived for free, but there is access to some of their excellent articles and some links to some really neat web resources that you can access by time period, theme or location.
Art and Images (British Museum). Stunning collection of online artifacts & exhibits including an amazing interactive timeline. Simply gorgeous & incredibly informative.
inudge Make your own music online. Fun! Cool!
SPIN via Google Books Search by keyword within issue or search the whole collection. Or browse by issue. Very cool.
UCSD Libraries anti-plagiarism tutorial This is really neat. I would *love* to do something like this, if only I knew how.