DarwinCatholic recently put up Michael F. Patton Jr's 1988 parody of trolley problems. For those who don't keep up with philosophy literature, Patton has a nonphilosopher's explanation page for a number of the references in it. He also gives a history of the parody, which is interesting in its own right and, as Patton argues, raises interesting philosophical questions about intellectual property.
In any case, the best thing was that sciencegirl rose to the challenge and actually diagrammed the problem. In her solution it looks like she's assuming for the sake of the problem act utilitarianism (either hedonistic or preference-based) without bells and whistles. In real life, of course, if a philosopher were to publish this explanation (at greater length and without the diagrams which make it worthwhile, no doubt), there would be an article in the same journal within a year arguing that what the problem shows is that you shouldn't be an act utilitarian but a rule utilitarian or an ideal utilitarian, or else that you should only be an act utilitarian in the company of such-and-such distinctions (i.e., bells and whistles). (This would change the unjust wars without war crimes / just wars with war crimes part of the analysis, for instance, and could have a big overall difference because of the fact that the brain on the trolley is a moral example for other brains, presumably also on trolleys; likewise, utilitarians who make a big deal out of intended and unintended consequences won't so easily block out some parts of the diagram as constant.) But, of course, that just is precisely part of what Patton was parodying. The awesome thing is the diagram.