Writer/illustrator Bradley W. Schenck has put a cool thing called the Pulp-O-Mizer on his Thrilling Tales of the Downright Unusual website. It lets you create pulp magazine covers with your own text, like this one I made of an alternate take on Kill All Monsters.
Once you've created your piece, you can save it in a couple of different formats, including one designed especially for Facebook. And if you really like what you made, you can order stuff with your cover on it, from posters to mugs to shirts to iPad cases.
I'm not getting anything for pimping the Pulp-O-Mizer; I just saw it and thought it was fun enough to mention.