Google has modified its robots.txt file to include a line which may signal the beginning of a new search feature — similar content search. This innocent looking piece of text ("Disallow: /relcontent") appears related to "Disallow: /relpage/" which has existed in the file for a very long time. Both (http://www.google.com/relpage/) URL’s (http://www.google.com/relcontent/) produce the same curious message when visiting — "Nothing."
You can see a list of related pages on Google. Just pass a query and this tool would enable you to search fairly broad topics. You can easily enter a paragraph or two of known information without picking and choosing the right keywords.