Google Keyword Tool is not bad.
Just remember it's not the tool to give you the numbers (yeah, I know there are some people using it for it), it's more useful when comparing different keywords so you can pick the ones with more/less searches.
It's also not bad for trending when you download the sheet and open it in excel... very useful when working on seasonal campaigns.
Also, the numbers are searches, so impressions no clicks, then remember that depending on niche/keyword total CTR won't be 100%, but 300%-400% (less or more, depending on keyword). <-- just realised you didn't ask for it, but was typing too fast... and maybe one will find it useful anyway.
MBlaster