I'm no expert when it comes to the best place to give money for relief efforts, whether it be the tsunami in Asia, hurricane Katrina, refugees in Sudan, etc., but I can give a list of some places that I know will use the money wisely ...
Compassion International: www.compassion.com
Red Cross: www.redcross.com
Doctors without Borders: www.doctorswithoutborders.org
Vineyard Community Church, Libertyville, IL: www.vineyardonline.org (no online donations, but the address is there so that you can make a check payable to Vineyard with "hurricane Katrina" in the memo line)