thumbs up for the word tracker(paid version). Overture? i don't think they still working. I only use seodigger to check those keywords rank on my site.
here are some tools:: http://freekeywords.wordtracker.com/ http://www.inventory.overture.com/ http://www.seochat.com/seo-tools/google-suggest-scraper/ http://tools.seobook.com/keyword-tools/seobook/index.php http://www.selfseo.com/keyword_suggestion_tool.php http://www.keyworddiscovery.com/ https://adwords.google.com/select/KeywordToolExternal i think the following will suit your requirement best:: http://freekeywords.wordtracker.com/
I also use different tools for different purposes, but to me the best single package would be Market Samurai
the best free keyword tool is the google adwords tool but when you are logged in to your adwords account i am working on a report to teach people how to do super fast keyword research using only free tools, hope it will be available soon
I use NicheBot from Nichebot.com, they have a free version but the paid membership is worth it and it's very valuable to figure out the daily/weekly/monthly traffic for specific KWs and how many people are competing for that KWP.
I find this easy to use and although not complete accurate paints a relative picture compared to other keywords! After all i find the numbers dont have be accuarte however as long as they are comparably accurate then it works!