A prime example of this is Google Search Engine Commands.These commands can be used by anyone to help you identify information regarding a website that enhances your chances for top Google placement. Here are a few of the commands I've used to improve my understanding of my very own website and the website(s) of my competitors:
Link: Locates links that are pointing to the site.
Site: Displays all of the pages indexed by the Google of the site.
Cache: Shows the last indexed and cached version of a site.
Info: Displays general information about a site.
Related: Shows potential competitors to a given site or site content.
You can use these commands for yourself simply by typing:
Link: http://www.yoururl.com
Site: http://www.yoururl.com
...and so on. Give it a try and see what information Google presents about your own website!
You may also be interested to know that some of these commands will also work with Yahoo and MSN.