Since overture is dead, I found
https://adwords.google.com/select/KeywordTool works well to get an idea about keyword searches from Google. Also, there is a box for "Calculate Estimates using Max CPC". Type in 5 as in $5 and all the results will show the dollar amounts of the max bids. Very interesting results and some results will show bar graphs of past months' traffic.
You need to log into your adwords account to use this tool.