Here are some Mississippi Red Cross websites, which also have some donation links at the sites:
Adams County Chapter of the American Red Cross
Oops, that's the only Miss. RC site which mentions Katrina AND has an evident donation button/link, I see. Oh well, so much for preparation and organization. --Here's the American Red Cross general donation link then, https://www.redcross.org/donate/donation-form.asp . That should do.
And here's the American Red Cross Southeast Louisiana Chapter, http://www.arcno.org/ ...whoops, there you actually have to create an account to make a donation. Sigh.
Well, the sites are informative if nothing else. At least they still exist, showing the servers haven't washed away, so that maybe Misty May and Kerri Walsh will have a beach to play volleyball on after all...