Practical SEO has compiled a list of useful SEO tools for you to use in your SEO campaigns. Some of these tools are free and some need a monthly subscription or a one time payment, but all of these tools are the best on the market and used by Practical SEO staff.
Free SEO Tools from SEO Book
SEOmoz Free & Premium SEO Tools
Raven Internet Marketing Tools 30 Days Free Trial
Free SEO report - Scribe SEO