Compete has some very powerful competitive research tool that you can use for keyword research and analysis.

You can find out things like how much traffic a particular website is getting and discover the keywords that are sending traffic to a specific site.

Just type in a keyword and see which websites get most of that traffic. John Reese even recommend this tool as one of its Traffic Secrets 2.0 best method.

You can pay to get a very detailed report on keyword competition or you can do with the free version.