Keyword Research Tools

http://spyfoo.com/
SpyFu lets you see which keywords your competitors are buying and which ones they optimize their site for.

http://tools.seobook.com/keyword-tools/seobook/
Powered by Wordtracker data, but has some great enhancements.

http://freekeywords.wordtracker.com/
Wordtracker helps website owners and search engine marketers identify keywords and phrases that are relevant to their or their client’s business and most likely to be used as queries by search engine visitors.

https://adwords.google.com/select/KeywordToolExternal
Google’s keyword tool – no account registration required.

http://www.keyworddiscovery.com/search.html
Keyword data is compiled and collected from a number of search engines to provide a far more accurate cross section of searches performed world wide.

http://adlab.msn.com/ForecastV2/
Forecast the impression count and demographic predictions using your selected list of keywords.

http://www.keywordcountry.com/
Predict your Adsense earnings before targeting a keyword!

http://www.wordze.com/
What keywords are being searched for and tools that will allow you to track keywords beyond their estimated daily search volume

http://wordtracker.com/
The de-facto standard in keyword research tools.

http://www.kwmap.net/
An innovative keyword search tool.

http://www.digitalpoint.com/tools/suggestion/
This is a handy little tool will show you the results of your query from both Wordtracker and Overture for determining which phrases are searched most often.

http://www.nichebot.com/
Keyword Research that gives you access to over 295 billion keywords in 41 languages spanning 243 countries using multiple keyword sources like Google, Wordtracker and Keyword Discovery.

http://www.iotaweb.org/
Free Google Adsense Keywords & YPN Keywords Search Tool

http://seodigger.com/
Seodigger works by building a reverse index of Google.

http://www.keywordspy.com/
Increase your Ad Campaign revenue by finding the most profitable keywords.Get access to over a billion keywords in our database.