As spotted by Hobo SEO, Google seems to be experimenting on updating it’s AdWords Keyword Tool which will allow its users to input 2500 keywords into the search box. Currently, the word limit is caped to a mere 100 in order to come up with new keyword ideas.
However, if you try it now it might not work for you as they are still working on it. While there is enough buzz hinting the same, the official word is yet to come out from Google.