I donated.
You should too.
I donated here:
http://news.bestfriends.org/index.cfm?page=specialreports&catid=04061773-BDB9-396E-9001EF6EC01318A4&mode=entry&entry=0A10958D-BDB9-396E-9686F524E4B3C132 Why them?
They're one of the main organizations that are coordinating animal rescue efforts in response to Katrina. They're all about the no kill philosophy. They have lots of good information on their website and seem both established and legit.
About them: (info taken from the organization's own website)
The mission of Best Friends is driven by the simple philosophy that kindness to animals helps build a better world for all of us. And the work of Best Friends is supported entirely through the donations of our members and supporters. Through the generous hearts and hands of people like you, we can ensure that animals who come into the care of Best Friends will never again be alone, hungry, sick, afraid, or in pain.
Our sanctuary, at the heart of Southern Utah's Golden Circle of national parks, is home, on any given day, to about 1,500 dogs, cats, horses, rabbits, and other animals.
In our home state, Best Friends manages a model No More Homeless Pets campaign with shelters and humane groups statewide to ensure that every healthy dog or cat that's ever born can be guaranteed a loving home.
And Best Friends reaches across the nation, helping humane groups, individual people, and entire communities to set up spay/neuter, shelter, foster, and adoption programs in their own neighborhoods, cities, and states.