This tool will give you the average search volumes for a particular keyword during a particular month, the exact
search volumes, the CPC and the advertiser competition for a particular keyword.

Using this tool you can find keywords on which to base a new blog that you would like to optimize for Adsense.  You look for high searches, a CPC rate of higher than $1.00 and for which there is alot of advertiser competition for this keyword (means lots of ads are available).

After you have found some keywords, you should then check to see how much competition meaning:  how many pages are already in the Google index that you would have to compete against.  If there are 6 million pages already in the Google search index, you’d better find another keyword.  6 milllion pages is going to be hard to beat.