Be warned: checking out this discussion of the worst songs ever recorded will result in a very nasty bout of earworms. Prepare yourself with an antidote then head on in. (Remembering that one person's antidote is another's deadly poison, I will not name my antidotes.)
Update 9/4/2009: J helpfully provides this list of bad songs for review and discussion. I'd say I'm in agreement with half to two-thirds of the list, but the absence of truly execrable '70s songs (including - don't click on it, don't even mouse over it, you've been warned, OK fine - The Song That Must Not Be Named) suggests a lack of either rigor or, at the very least, direct personal experience of the 1970s as expressed via AM radio. Or it might just be self-preservation.