The team at E2M is taking this opportunity to analyze other significant (and free to use/try) keyword research tools out there. We are asking ourselves what data and logic should ideally go into keyword research, how this logic can be programmatically applied to the creation of tools, and what the best ways are to consolidate and use their output. Here’s a quick look at 25 other keyword research tools, some well-known and some you’d do well to know. These are not alternatives to the AdWords Keyword Tool on their own, but each of them performs some function of the AdWords tool in its own unique way, and all of them aid and abet your keyword research quite well.
In a nutshell, Long Tail Pro helps you quickly find keywords in bulk based on a seed keyword that you input.  In addition to returning hundreds of related keywords, the tool also shows search volume (monthly search volume), advertiser bid, number of words, rank value, and my favorite Keyword Competitiveness (helps you judge the competition and keyword difficulty).