From the FEMA website posted on September 4, 2005 (http://www.fema.gov/news/katrinanews.fema):
The Department of Homeland Security's Federal Emergency Management Agency has established a toll-free Hurricane Katrina hotline to accept public contributions of goods and services to assist victims. The hotline, 1-800-440-6728, has been activated and has begun receiving calls from around the nation and the world.
A list of organizations active during disasters can be found at the USA Freedom Corps website, www.usafreedomcorps.gov.
The hotline does not itself accept donations and is not designed to accommodate emergency or information resource and it cannot assist those wishing to do business with the agency. For more information on this please visit www.fema.gov/ofm, or contact FEMA's acquisition voice message system at (202) 646-4006.
FEMA also has activated the National Emergency Resource Registry to coordinate donations from businesses willing to assist with major needs such as housing, transportation and supplies. Businesses can access the database at www.fema.gov and click on the "Help the Victims of Hurricane Katrina" or www.swern.gov to register to provide relief.