Has anyone used the keyword search tool yet in Yahoo? It hides behind "add keywords" once you clicked on an ad group. You need to enter a URL in the blue box, then add one or more keywords in the biggest field. You can specify words that must appear in each keyword or phrase and you can also specify negatives. The results will give you keywords relating to the site with estimated monthly searches. You can also refine the list by choosing words you would like to keep and do further searches from there.
For different languages simply enter a URL with .de or .fr.
I believe the tool can still be improved though by Yahoo...
Let me know if this is or isn't of any use for you.