Yep, .
Wordtracker kicks ass.
You type in a seed phrase like 'teen porn' then it does a search on the search engines for that, and finds loads of related keywords also used by those sites that are found.
For each of these related keywords, it tells you how much it was searched, and how much other webmasters are targetting these words, plus its own calculation which are the best keywords to target.
This and
Web Position Gold (which does everything else that wordtracker doesn't do), are the only 2 search engine tools I use.