Many, many people on the Web have cited and discussed this Michael Lewis piece, "The End", on our current financial problems, but in case you haven't seen it, I recommend it. As noted here earlier, a key element in making the problem so big and hard to contain seems to have been the terrible performance of the ratings agencies:
But Wall Street had used these BBB tranches—the worst of the worst—to build yet another tower of bonds: a “particularly egregious” C.D.O. The reason they did this was that the rating agencies, presented with the pile of bonds backed by dubious loans, would pronounce most of them AAA. These bonds could then be sold to investors—pension funds, insurance companies—who were allowed to invest only in highly rated securities
I've seen fewer people comment on this second Lewis piece, "Bonus Jackpot Can Be Yours in Five Easy Steps", but it's also quite good. Stay away, though, if you don't like really black humor.