I know another great site forAdSense....
Free AdSense Web Tool
I dont necessarily recommend anyone starting out cheap or on the cheapest words, I do recommend starting out on google and overture to guarantee higher traffic quality.I also recommend starting out on really well targeted words and ads.
Here is my overturetip:Build a big keyword list as exact match listings list above broad match listings
Best Google tip:Always try to get a high clickthrough rate to lower click price after click through rate kicks in (1000 ad impressions on google for that keyword) !Hope this help to newbies out there who are new to PPC .