Google Hacks Video Halla from
Information Leak published three videos show people how to put some useful strings and find interesting pages.
Basically, it's using application specific + unique data embedded in the URL or HTML to find sites uses those applications. The search string find other people's security camera backend is creepy(and cool) :yes!:
(Hacking into someone's FTP is also easier with Google's help)
Check out these three
Google Hacks 1Google Hacks 2Google Hacks 3