Here's a great blog - summarizing the jumble of places that are available for sending donations for Katrina relief. Check there before mailing anything - it may save you some money or resources, or give you new ideas.
Today I went past the location where they were collecting where I had dropped off bags of baby stuff yesterday and there was a big banner up (apparently printed fast at the print shop located right there) that read: "You're the GREATEST * Katrina relief collection huge success". That made me feel good. It's nice to hear about one little success, after so much tragedy and failure.