Not much in life is free, but these tools are, and they’re very good. Enjoy.

1. SEO Book Keyword Suggestion Tool – Excellent keyword research tool featuring regional search volume estimates, bid prices, semantic variations and more.
2. Xenu Link Sleuth – find broken links and get a thorough overview of a sites linking structure.
3. SEOMoz Page Strength – Makes a reasoned guess as to the value of a page. Good for comparing the relative value of various web pages, which is useful when trying to determine the value of a link.
4. Google Keywords External – query Google’s Adwords database to generate keyword lists.
5. XML Sitemaps Generator – generate sitemaps for use with Google’s Webmaster Central.