The U.S. Administration on Aging is an excellent resource for statistics, policy updates, and general information on activities related to the American aging population.
The online version of the Encyclopedia of Gerontology
The American Geriatrics Society is an excellent resource for material related to aging and health care.
The American Association of Retired Persons website provides a wide variety of resources to older adults who are over the age of 50. It is worth it to look around a bit and become familiar with the site. Lots of goodies hidden behind some of the links.
The Merck Manual Of Geriatrics provides information on working with older populations, disease prevention, Federal health care funding, issues related to provision of care, quality of life and social issues in older adults.