Googles search based keyword tool is great for finding better paying adsense keywords for a website! You an put in your website url and google will give you a list of keywords and the ppc value of each of them. Check it out here: https://adwords.google.com//ko/KeywordPlanner/Home#
The tool works best with websites associated with your google adsense account. It will still give you results if the website is not associated with your account but the results are more limited.
The tool does however work really well with foreign language sites. Having tested it on a few of my Spanish websites I have found that it provides a pretty good list of suggested words for adsense purposes.