Google Site: Operator

The site operator is a command in Google that allows you to search all the indexed pages of a given site. Say you wanted to look at every page on the BBC website – type site:bbc.co.uk into Google to generate results pages of exclusively indexed URLs at bbc.co.uk. For searching within a site, you can type site:bbc.co.uk + widgets, to look for references to the keyword ‘widgets’ throughout the source site. This is incredibly useful for looking at competing sites in more detail, so you can get a feel for how your competitors are approaching their search engine marketing.

http://www.google.com/insights/siteoperator/home