A photographer who went through the Katrina disaster has posted a spectacular slideshow of the images he took throughout the 5 days he was there. It will give you quite a different impression than what the media has provided, and makes much more understandable what happened. And much less excusable the reaction on the part of the authorities.
It's a little long, but I very much recommend going through the whole thing. Once you get started, you won't be able to stop.