Flickr has a great pool called Gee, That Looks Terrible! which features thousands scanned ads for food products and from recipe books from the 40s-70s. My favorites are the slightly off-color masterpieces like this one from Glen.h, which look suspiciously like someone's already digested them.
Other favorites include the California Curry Platter, Pizza in a Skillet, and this monstrous ring of gelatinous goop topped with a Spam knock-off called Mor, a "mild-spiced pork meat for a jolly snack!"
Or how about this "Party Potato Salad" from user Charm and Poise?
Just to prove that horrible cooking doesn't just belong to decades past, though, check out this recent clip from the Food Network: