Site map providers are the backbone to navigation menus seen throughout websites. They are the connection between the data source and the actual navigational menus that are referenced in a site’s master page. SharePoint 2010 includes several site map providers, which are explained in this section.
For additional information on site map providers, see “Site Map Providers” at http://msdn.microsoft.com/en-us/library/aa478951.aspx.
You can find out-of-the-box SharePoint 2010 site map providers in the Web application web.config file located on the Web front-end server under %SystemDrive%\inetpub\wwwroot\wss\VirtualDirectories\[portnumber]\web.config.
See the book’s resource site for listings of the site map providers ...