Medicare.gov is a useful new government sponsored resourse that provides data evaluating nursing homes that have been certified by Medicare and Medicaid. The site has a general search engine, as well as one that permits users to locate nursing homes by state. In addition, the site also provides links to state sponsored data on nursing homes.
See also this related site, The Health Insurance Portability and Accountability Act of 1996 (HIPAA) which includes information on coverage, and laws and regulations.