There are a number of keyword research tools that can help you find keywords that are frequently searched for but not overly used.
Apart from the Wordtracker, there are some more equally important research tools like the Overture, Google AdWords Keyword and Guidebeam.
Overture's
Advertising Your Business with Yahoo! Search Marketing keyword suggestion tool is free and quicker than Wordtracker. It works like the Wordtracker but doesn't tell you how many websites are targeting each keyword phrase. If the word you keyed in is not a common search term then you will not get any results. It means that very few people have actually searched for that word during the last month.
Even Google Keyword Tool generates potential keywords for your ad campaign and reports their Google statistics, including search performance and seasonal trends. Features of this tool include,
Sorting the results of your desired keyword search by popularity, past performance history within the AdWords system, cost, and predicted ad position.
Easy keyword manipulation where you can select a few keywords here and there or add them all at once.
Searches for keywords present even in any webpage URL specified by your search. It can also expand your keyword search even further to include those pages that are linked to or from the original URL page.
More keyword results are generated based on regularly updated usage statistics database. This helps you to get new keywords or phrases.
Guidebeam
guidebeam.com is an interesting resource. Type in a phrase and it will suggest a large number of related searches. The numbers generated against each phrase are Guidebeam's estimation of how relevant that phrase is.
These softwares are useful for researching how people search the web and then optimizing your own web pages so that more people find your web site.
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Some Keyword Research Tools 
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