Larwee has a good thread with several, mainly free KW tools.
Keyword selection tools
I've been doing lots of research to try to find the best KW tool to buy.
With the free ones you can do one thing here and one thing there
but it's too scattered and time consuming.
Each of the paid kw tools seem to have their own strengths and weaknesses.
At this point I'm leaning toward Keyword Elite but have not made my final decision.