Google Trends

This powerful tool helps you to see the trend of your preferred keywords around the world.

http://www.google.com/trends

Keyword Density

See the strongest keywords of your site at:

http://www.webuildpages.com/

Search Engine Optimization Tools

These tools offer help and guidance in the ever-changing world of search engine optimisation.

• Keyword Research Tool
• Search Engine Position Checker
• Link Popularity Checker
• Keyword Analysis Tool
• Search Engine Spider Simulator
• Meta Tag Generator
• Web Page Analyser
• Top PPC Bids Checker
• mod_rewrite RewriteRule Generator
• Link Appeal
• Class C Checker

Use them at:

http://www.webmaster-toolkit.com/search-engine-optimisation-tools.shtml

Keyword Popularity Checker

The Keyword Popularity Checker provides statistics on how often your keywords and phrases are searched in major search engines.

http://www.freewebsubmission.com/keyword-popularity.html