Keyword Tools

https://adwords.google.com/select/KeywordToolExternal
The AdWords Keyword Tool is designed to help you generate new keywords,
based on the words or phrases that you enter into the keyword generator.
This is another of those tools that, although it was built specifically with
AdWords in mind, might also prove useful for AdSense types as well.
One particularly useful feature of the Keyword Tool is that it lets you enter
the URL of a specific Web site to see what keywords are generated, according
to the content of the site. With it, you can enter the URL of the page you’re
optimizing for AdSense ads to see what keywords are being recognized on
that page.
The Keyword Tool is a great way to make sure that your page is being recognized
for the keyword ads you’re targeting. As an added bonus, it has a neat
little progress meter at the bottom that processes while it’s examining the
page that you entered. I know . . . small things for small minds, which mine
definitely is at times!
The results that are returned when the page is finished processing are pretty
comprehensive. You’ll probably see the keywords you’re targeting as well as
some that you hadn’t thought of. All in all, a very useful tool.