Yahoo:"http://inventory.overture.com/d/searchinventory/suggestion/" Google:"https://adwords.google.com/select/KeywordToolExternal"
I did a post recently about the top 6 keyword tools, where I break down the best free tools to help you out. I hope it helps.
There ya go: http://inventory.overture.com/d/searchinventory/suggestion/ http://www.marketleap.com/verify/default.htm http://www.markhorrell.com/tools/density.asp http://www.seochat.com/seo-tools/keyword-cloud/ http://www.seochat.com/seo-tools/keyword-difficulty/ http://www.seochat.com/seo-tools/keyword-optimizer/ http://www.iwebtool.com/keyword_suggestion http://www.apogee-web-consulting.com/tools/keyword_tool.php
I'm trying to stick together a tool that takes a different slant on keyword analysis. It can take take a list of search terms and estimate which ones will be easiest to optimise a webpage for. For example, this page looks at the high paying list from here, and produces a report that estimates which of those terms should be less competitive in terms of SERPs. As far as I know, none of the other free tools do this.