In particular, dark chocolate is good for you, according to an article in Reuters that cites research recently completed at the Athens Medical School.
According to the article, the heart-protecting properties of dark chocolate, which contains high levels of a kind of antioxidant called flavonoids, have been acknowledged for some time. But the latest research sheds new light on how the mechanism might work, by protecting blood vessels from the damaging effects of unstable oxygen compounds called free radicals.
The study only involved 17 health volunteers, alas, so there is more work to be done. Perhaps I can sign up somewhere.
Also, apparently it is only dark chocolate in which this effect is seen. Something in the milk apparently interferes with absorption of the good chemicals.