US Dept. of Health & Human Services

http://www.hhs.gov/

Centers for Medicare and Medicaid

http://www.cms.gov/default.asp

CAQH

http://www.caqh.org/

Blue Cross Blue Shield

http://www.bcbs.com/

Aetna

http://www.aetna.com/

Humana

https://www.humana.com/

United Health Care

http://www.uhc.com/

USPS Zip Code Locator

https://tools.usps.com/go/POLocatorAction!input.action