Hurricane Katrina

This may be the most destructive storm in U.S. history. Here's one page with links to most of the reputable charities operating in the area:
http://www.networkforgood.org/topics/animal_environ/hurricanes/?

The website above, like other centralising websites, takes a 3% cut of one's donation, so it's better to find a charity that one likes at the above, then donate directly via the charity's website.