http://www.keyworddiscovery.com/search.html

In order to find popular keywords for your site pages simply type a key phrase and the tool will generate the top 100 keywords for you. By clicking on the analyze button you can further know total searches, its number of occurrences in database and its daily predicted count.

Additional options:

X-ref: If you use this option and input any website name, say your competitors site name, then it will show the common keywords from your search results and its count being used on competitors site.

Industry terms: Shows top keywords and total searches that is driving traffic to a particular industry category.