There are numbers of good organizations through which you can donate to help the victims of Katrina. The Red Cross is not one of them. Given their history of mismanaging funds following 9/11 and their refusal to repudiate the racist remarks of Kayne West made on their behalf, I strongly encouarge you to not support them.
If you'd like to know for sure where your money is going, you can consider helping a local church congregation. I have one to recommend to you: Lakeshore Baptist Church This church is pastored by a man I know and can personally recommend for his integrity. He lost his home, along with the homes of every member of the congregation, and their church building as well. As you can see at their website, the damage is beyond description. We sent them a donation, and I'd like to encourage any and all of my readers to join in helping them rebuild the lives of their church members. There's a PayPal link at the site so you can give without worrying about mail service. Thanks for helping.