I think most people understand now that the Louisiana government was simply incompetent when faced with Katrina. But with FEMA, I knew about them not getting to the convention center until days after it had turned into a third world country. And, I knew FEMA should have been more pro-active urging New Orleans to evacuate. I suspected there was more, but this is the best explanation of how FEMA screwed-up that I've heard yet:

http://www.npr.org/templates/story/story.php?storyId=4849706

You have to click on the listen button at the top to understand the extent of the fuck-up.