I'd like to recommend a fun little piece called the The Schizophrenia of Modern Ethical Theories (PDF), which points out that popular moral theories look very strange when actually applied as a grounds for action in real-life situations. Minimally, the author argues that certain reasons for actions are incompatible with certain motives, and that this becomes incoherent if we suppose that these motives were (at least partially) the motivation we had to adopt that set of reasons in the first place.

For example, if you tend to your sick friend, but explain to them that you are (really only) doing so on utilitarian ground, or on egoistic grounds, or because you are obligated to do so, etc, well...doesn't that seem off? And don't those reasons for action, presumably a generalization of a great deal of specific situations of this sort, seem incompatible with the original motivation that we felt was morally good?