Someone's posted the whole of June, 1938's Action Comics #1 (including the first funnybook appearance of Superman) to the web as a series of medium-resolution scans. Link (Thanks, Eyes Spies and Lies!)) via [Boing Boing]
I've never been much of a comic book fan, but this is pretty darn great. It's filled with grammatical errors, plot "developments" that take all of two panels to cover, cliffhangers... And I have to say that some of the art is pretty fantastic, too (like the "... Run faster than an express train ..." panel shown here).