Spyfu

This is the best keyword tool I have ever seen. PPC advertising is a quick traffic generator. Because it costs money, people make sure they have the best keywords and are paying only for the ones that drive in the buyer with a credit card in hand.
This site gives you all of their research! You have 2 options when using Spyfu to hijack the research of your competitors:
Type in a keyword term – this gives you the average cost for the term, daily budget, similar terms, adwords results, organic results, directory categories, and more. By checking the similar items, you will be able to get other terms that companies are paying for along with your main term.
Type in a domain name – By typing in the domain of one of your competitors, you can find the exact keywords they are using in their pay per click campaign. It literally hands you their
months of keyword research for free!
By combining Spyfu with other keyword research tools, you
will know exactly what to optimize your site for. The information you get at Spyfu will blow away all other tools, though. All you have to do is find someone in your industry that has been around for some years. You can be sure that they've adjusted and tweaked their campaigns to the
fullest over time. Now you get to take their research and save yourself years of time!