The Amateur Radio Emergency Service (ARES) is a nationwide field organization sponsored by the ARRL and composed of licensed amateur radio operators who are willing to offer their time and equipment to provide communications support for local governments and non-profit disaster relief organizations during disasters and emergencies.
For more information about ARES as a national organization, go to: http://www.arrl.org/FandES/field/pscm/sec1-ch1.html