Here are some free high paying keyword lists I have found. If you are going to build sites for adsense they might come in handy. Keep in mind that it’s against Adsense TOS to build pages solely for the purpose of displaying adsense ads.

http://www.sorve.com/adsense.htm – A bit outdated in myt opinion.
http://www.googlest.com – You have to make 30 posts in their forum or pay $10 for this one. They are a good resource.
http://keywords.clickhereforit.com/

If you know of any other good lists, leave a comment and let me know.