Ranking Checker by SEOmoz.com

This tool allows you to type up to 5 keywords a day. You will not be charged by using this tool and it is very easy to use it. First, you have to open an account in SEOmoz.com. After you sign in to the website, choose 'browser button' and it will help you copy the URL page that you type before automatically.

MultiRank Checker by iWebtool.com

Using MultiRank Checker you compare your Google PageRank and Alexa ranking from your own website and against all your competitors.

Spider Viewer at http://www.webuildpages.com/seo-tools/spider-test/

This tool will let you see your website as a spider sees it. This tool is helpful for analysing your internal links, your meta information and your page content.

Keyword Density at http://www.webuildpages.com/seo-tools/keyword-density/

This tool is helpful in balancing your keywords within your content and ensuring the right keywords appear on the pages they're intended.

Header Checker at http://www.webuildpages.com/header-checker/

Use this tool to check any web page's header tags. Make sure your pages are returning the correct status codes and that your redirects are working properly. Since incorrect redirects can be a cause of indexing and/or ranking problems, it's a good idea to check that all your HTTP status codes are correct.

Search Combination at http://www.webuildpages.com/search/

In each list, please enter a group of words or phrases that are related. For example, list one could be a group of colours, and list two could be a group of things. This tool will generate all possible combinations of the two lists, with one phrase coming from list one, and one phrase coming from list two.

SEO for Firefox by SEOBook.com

Want to know why Google or Yahoo! ranks pages? If so this is the Firefox extension for you. SEO for Firefox pulls in many useful marketing data points to make it easy get a holistic view of the competitive landscape of a market directly in the search results.

Google Analytics / Google Webmaster Console by Google.com

Free tools from the search provider with 90% market share for web searches. You MUST use these!