I've read quite a bit about hurricane Katrina in the last few day, some good and some very poor. The worst was a supposed Christian website claiming that the hurricane is God's judgement on New Orleans. Where these people get this rubbish from is beyond me! If this really was God's judgement, then things would be significantly worst than they are right now! Read the book of Revelation for full details!
I believe that hurricane Katrina is merely part of the make-up of the world in which we live, after all, Jesus himself said that "In this world you will have trouble. But take heart! I have overcome the world." John 16:33b This is a simple statement and promise which we as Christians have to accept. I believe that hurricane Katrina is simply part of those troubles that Jesus was referring to.
In the good stuff I've read about Katrina, I came across Hurricane Katrina Refugee Blog which is the author's personal account of a family's experience with Hurricane Katrina. It is definitely worth reading.