Healthcare.gov
This site directs you, based on your state of residence, to purchase insurance through either the appropriate state or federal health insurance marketplace.
CDC Healthy Living site
The Centers for Disease Control's (CDC's) healthy living site covers specific health conditions, health at different life stages, and health considerations for specific populations.
Medicare home page
Medicare is a health insurance program for people aged 65 and over who have paid into the system through payroll taxes on their wages. In order to receive benefits, you need to enroll. This page, getting started with Medicare, gives more information about setting up Medicare.