Wordtracker is an online keyword research tool that helps web site owners, Webmasters and search engine marketers identify keywords and phrases that are relevant to a web sites based on queries by search engine visitors.

Wordtracker is subscription based tool that can be purchased for an annual fee of $329 US. There is also a free trial that users can test out for seven days.

Wordtracker results are based on metacrawler data as opposed to actual data from search engines. Results provided are based on previous month's activity which provides an estimate of what people are searching for on the Web. It is estimated that WordTrackers database contains more than 350 million search terms that are updated each and every week.

Other WordTracker Resources

WordTracker Blog - http://www.wordtracker.com/blog/
Free Keyword Suggestion Tool - http://freekeywords.wordtracker.com/