The following SEO tools are excellent resources to learn more about SEO:

• http://www.gritechnologies.com/tools/spider.go - see your site like google does
  
• http://googlerankings.com/ultimate_seo_tool.php
• http://googlerankings.com/kdindex.php
• http://www.mcdar.net/KeywordTool/keywordtool.asp - very good, shows your site and then comparison with the top for the given keyword.
• Google Monitor - monitor your position in google searches.
• Overture Keyword Selector Tool - identify keywords and their query popularity as defined by overture.
• Overture Tool - identify keywords and their query popularity as defined by overture.
• Seatch Multiple Google Servers - see what multiple google servers return