SEMOServices | Free Search Engine Optimization Tools I recommend for Do-It-Yourself SEO are:

Backlink Builder – This tools searches for websites of the theme you specify that contain keyphrases like “Add link”, “Add site”, “Add URL”, “Add URL”, “Submit URL”, “Add Article” etc. Most of the results could be quality potential backlinks.

Backlink Summary – This tool will give you a summary of your competitor’s backlinks.

Domain Stats Tool – This tool helps you get all kind of statistics of your competitor’s domains. The statistics include Alexa Taffic Rank, Age of the domains, Yahoo WebRank, Dmoz listings, count of backlinks and number of pages indexed in Search Engines like Google, Yahoo, MSN, etc.  It will probably help you figure out why some of your competitors are ranking better than you.

Keyword Density Check – This tool will analyze your chosen URL and return a table of keyword density values for one-, two-, or three-word key terms.

Keyword Position -This tool features an optional language/country selection option, which allows you to receive more specific results for your criteria and observe activity by demographics.

Link Popularity – This tool will query all the major search engines (Google, Yahoo, and MSN) when you enter the “link:” operator with your chosen URL.  It will return the total link count for each URL.

Metatag Analyzer – This tool will analyze a website’s meta tags. Although the use of meta data is certainly in question, analyzing a competitors “keyword” and “description” meta values is a good way to find ideas for key terms and effective copy for your website.

PageRank Lookup – Enter a list of URLs and it will return the PageRank value for each URL.

Reciprocal Link Check – This tool will provide a reciprocal link count per domain.

Site Link Analyzer- This tool will analyze a given web page and return a table of data containing columns of outbound links and their associated anchor text. If a hyperlink is represented by an image, the image’s alt attribute will be included as the anchor text.