Below you’ll find five of the most popular free keyword research tools on the internet. However, it takes more to come up with the right keywords for your purposes than just choosing a related word or phrase and seeing how it shows up in searches most often. You need to determine a lot of other factors before targeting that word for an SEO campaign. For just two examples, you should know something about how many sites are competing over traffic for that keyword and how likely searches for that phrase are to convert into actual sales.
Google AdWords Keyword Tool–Even if you don’t have an AdWords account, you can use Google’s keyword tool. You can search by word, phrase, website or a variety of other options. You can also localize your search, seeing results for just a specified geographic area (e.g. Japan).
Wordtracker–Wordtracker’s free keyword tool is a little harder to find from their homepage now that they seem to be emphasizing more paid services, but it still exists. It will give you the top 100 search terms for any word or phrase with the number of searches run, but no other data.
Keyword Discovery–Pretty much the same as Wordtracker’s free tool, again showing the top 100 results unless you pay for more results with the premium service. Both engines give you results from the last year, but Wordtracker specifies data from the US, whereas Keyword Discovery uses a global database.
SEO Keyword Tool–You need to sign up for a free account before using this tool. It breaks down Wordtracker’s results by specific search engine. It also gives information on Google suggestions for keywords and a few other useful tools.
Wordstream–Instead of giving you counts of the number of searches run on keywords or phrases, this tool gives you a small bar graph for each result indicating the “relative frequency” of that search.