There are a number of free online resources that provide databases for finding graves. About.com offers a comprehensive list of Internet resources for finding burial sites, including FindAGrave.com. This site offers a number of search options and a database covering millions of grave records.
The National Cemetery Administration offers a map of national cemeteries and state veterans cemeteries, and can be found on the U.S. Department of Veterans Affairs website. Another excellent resource for finding burial sites is the website detailing Arlington National Cemetery's graves. The website even offers information regarding funerals and historical figures buried in the famous cemetery.