If you look at the difference in traffic between google and overture, you can reasonably guess that those numbers should be multiplied by 14 to get the number of searches on google.

And that doesn't even scratch the surface of keyword permutations. I use this tool to create PPC keyword lists:

http://www.keyword-helper.com/

The tool takes separate lists of keywords and compiles them into thousands of possible permutations, and then I feed those keywords into my PPC ad campaigns.

I frequently find unexpected versions of the keywords are popular search queries in real life. "Product life cycle management" might become "life cycle products software", for instance (searched 119 times on Google last month). Complex keywords (3 words or more) have very large fringe tails like this. There are literally hundreds of permutations like that that are getting hundreds or thousands of searches per month.

Thanks for the thoughts. I didn't know the multiplier was 14 - I always assumed 2 or 3. Your comments on longer search phrases is very good, and because few companies take the time to discover and manage these their not only richer but less competitive. - Craig

Thakns, I too did not know about the 14 multiplication, though it was like 7.

Don;t forget that there is alos another really good keyword generation tool out there that also shows you a sampling of search activity.
http://www.wordtracker.com