Free keyword research tools

WordTracker is a research tool that will give you the keywords you need to rise above your competitors in search engine rankings. It will show you how keyword research can help you discover untapped market niches, get inspiration for new products and create content that distinguishes your site from the other websites. It has a free and a fee based service that provides you with a list of related keywords and the estimated search volume for each keyword from two search engines, dogpile.com and metacrawler.com which makes several million searches per day.

Google AdWords Keyword Tool is a free tool that will give you keywords based on what searchers are entering in Google search. It  will give you the amount of advertisers bidding on each term within the Google AdWords Program. It will help you because it's data from the Google AdWords Program and not the entire internet.

Keyword Discovery is another keyword research tools that compiled and collected data from a number of search engines to provide a far more accurate cross section of searches performed world wide and generate the top 100 keywords for you.

Overture Keyword Suggestion Tool is intended to help optimize pay per click campaigns on Yahoo!, but its also very useful to discover keyword for your search engine optimization. It  will give you the total number of times a search query has been entered into a search engines with-in the Overture network in the previous calendar month. The Overture network includes searches from Yahoo! Search, AltaVista and MSN as well as others search engines.

It's up to you to use which keyword research tools suit your needs.