There are two major organizations that provide emergency communications nation wide.  ARES (Amateur Radio Emergency Service) sponsored by the ARRL, is available to serve hospitals, The American Red Cross, The Salvation Army and other such groups as well as the National Weather service.  Meanwhile RACES (Radio Amateur Civil Emergency Service) operates at the pleasure of various state and local government during civil emergencies.  Links include:

ARES (Amateur Radio Emergency Service)

RACES (Radio Amateur Civil Emergency Service)

ARRL - ARES vs RACES Frequently Asked Questions

Anne Arundel County - ARES / RACES

Prince George's County - ARES / RACES

Howard County - ARES / RACES

Calvert County Auxillary Communications Services