A couple of quick links to pass along:
green_key has generously offered to make LJ icons of any kind for those who donate to Katrina-related charities.
Because many of the evacuation spots won't take pets, the Humane Society of Northwest Louisiana has partnered with the Louisiana Veterinary Medical Association, the Krewe of Barkus and Meoux, Caddo Caring Canines, and Animal Welfare, Inc. to set up an emergency shelter for pets of all sizes at no charge. They are doing some good (and unsung) work, and could use support. (Thanks to agentxpndble for making me aware of this.)
Likewise, Noah's Wish is a not-for-profit, animal welfare organization with a straightforward mission: they exist to keep animals alive during disasters. They have deployed a team to Louisiana, and they are also seeking and deserving of support. (Thanks to green_key for making me aware of this.)
And here's a word from Belmont University, my institution: Belmont University Offers to Admit Students Displaced by Katrina: Will send tuition payments to students' home institutions.
Additional links about how to help, especially if you're in the Middle Tennessee area, can be found here.
"No one but Night, with tears on her dark face,
Watches beside me in this windy place."
~Edna St. Vincent Millay