[smn2]

... and you might like to try the following resources too:
https://adwords.google.com/select/KeywordSandbox
http://www.digitalpoint.com/tools/suggestion/
http://www.wordtracker.com
http://www.espotting.com/popups/keywordgenbox.asp
http://www.keywordsfinder.com/ (purchase required)

I think the paid-for version of Wordtracker may be your
best bet, but I'm sure others have got opinions too.

Personally, I like to see what people are searching for on
Google

Steve