Great keyword research tool

This is great keyword research tool you can use together with google keyword tool:
http://www.keyworddiscovery.com/search.html

Yet another 2 even better tools:

This tool is great, can be the best free tool I came across.
The Free Keyword Niche Finder - WordStream's Niche Keyword Research Tool

The Free Keyword Tool from WordStream - Free Keywords for SEO, AdWords, & Blogging

Theo mantablog