I'm reading a couple things in order to add an extra angle to my previous Foucault/financial-meltdown paper. Robert Benne's The Ethics of Democratic Capitalism provides an interesting framework from which to analyze business/economics from a Christian standpoint. His framework uses Niebuhr and John Rawls as the two primary thinkers. Niebuhr's primary work on the relation of the Christian to society is find in Moral man and Immoral Society: A Study in Ethics and Politics.
In some ways, this work is similar to a movie whose trailer tells you the whole story. The title itself basically lays out the thesis -- individuals are much more likely to behave morally than groups. Even though groups are made of a individuals, something happens within that interaction that enables groups to do things the individual members would never approve of. The larger the group, the bigger the difference in morals as well. Niebuhr links this to an innate will-to-power related to his vision of Original Sin. The theological background for much of his ethical concepts can be found in The Nature and Destiny of Man which I have sitting on my bookshelf waiting to be read. Suffice it to say that Niebuhr views pride as a sin of idolatry. It is difficult if not impossible to shed this as an individual, but impossible to shed as a society.
Those interested in this book but shy away from it's length (277 pages) would not miss much if they skip some of the chapters in the middle. In my opinion, chapters 5-8 can be skipped without missing much. These chapters offer somewhat dated analyses of class struggle and a very-much-dated capitalist/socialist dichotomy which can become a bit burdensome. This isn't to blame Niebuhr -- at the time it was written, these issues were front page news. I wouldn't expect him to predict the fall of communism and the rise of oligarchic capitalism which has in many ways replaced socialism as the "second in line" to traditional capitalism. The question no longer is capitalist or socialist as much as it is unfettered capitalist or regulated capitalist. I think Niebuhr would laugh at some of the common sense regulations which get labeled capitalist these days.
While Niebuhr's work is definitely located in its time period, I'll close by pointing out one amazingly prescient paragraph. Niebuhr was obviously an influence on Martin Luther King, Jr., but Niebuhr's almost uncanny prediction of the civil rights movement is startling:
The technique of non-violence will not eliminate all these perils [discrimination]. But it will reduce them. It will, if persisted in with the same patience and discipline attained by Mr. Gandhi and his followers, achieve a degree of justice which neither pure moral suasion nor violence could gain. Boycotts against banks which discriminate against Negroes in granting credit, against stores which refuse to employ Negroes while serving Negro trade, and against public service corporations which practice racial discrimination, would undoubtedly be crowned with some measure of success.