"I rarely get excited about SEO and SEM tools...But, when it comes to keyword research it is virtually impossible to produce a quality worksheet without software. When I have to perform the same task for my customers, the process is even more daunting and time consuming...there is now a better way to manage huge keyword lists and this tool is called WordStream."
This tool was originally created to carry out keyword research for paid campaigns using Google's AdWords platform. However, it can also be used to research organic keywords, providing estimated global/local monthly search volumes for keywords (i.e. their popularity) and their competition (i.e. how difficult they are to rank for) for organic search.
Wordstream is a free keyword tool that makes it easy and fast to get those keywords that your business needs most in order to drive traffic through paid and organic search. All you need to do is enter a website URL or keyword and you will get hundreds of relevant keyword results that are tailored to your country or industry. Every keyword has an estimated CPC, competition score, and a proprietary opportunity score that will assist you in budgeting for your online campaigns. You can download your list in a CSV format and upload it in AdWords directly and begin to work on your new campaigns.
Long Tail Pro is a keyword research tool that helps you quickly find low competition keywords for your website. In particular, the tool is built for people doing SEO (search engine optimization) as opposed to people doing paid ads (Google Adwords PPC). I'm sure there are some advertisers that use the tool for paid ad keyword research, but the tool was built for SEO keyword research.