And now for a public service announcement. Disasters can bring out the best in people, and the worst, and one unfortunate effect of shaking things up as much as Katrina did is that many of the bottom feeders have risen to the surface. If you recieve an email, no matter how legit it looks, that claims to be from a charitable organization, please check them out before donating. And even then don't use any links from unsolicited emails. Any legitimate group will have their own website that you can find through any search engine.
Even if an email looks like it came from a real organization, that's no guarantee. These phishers have gotten pretty good at faking the look of real banks and other institutions in an attempt to bilk people out of their money. Often the only give away is some extra stuff in the email address. Your best bet is to go the organization's home page by yourself, and then make your donation.
Hope this helps.