From SEOBook you can get a wide array of free and paid SEO Tools for SEO professionals and do-it-yourself webmasters.
If you are serious about search engine optimisation, then Wordtracker is a good investment, its' a good resource for any search engine marketing professional.
SEOmoz' tools are good all-round tools to help with keyword rankings, monitor your competitors, and analyze your sites‚Äô content.
Search for copies of your page on the web and make sure your content is unique with this tool from Copyscape.
Keep, share and discover the best of the web using delicious, the worlds leading social bookmarking service.
The Webconfs tool displays the approximate age of a website on the Internet and allows you to view how the website looked when it first started.
WordStreams suite of free keyword tools is the easiest way to improve the quality of your keyword research.
Alexa gives you free traffic metrics, search analytics, demographics, and more for websites...
This validator tool from W3C checks the markup validity of Web documents in HTML, XHTML, SMIL, MathML, etc.
TubeMogul is a video distribution service for brand advertisers who want to easily send their videos to the top video and social networking sites.
Link Assistant has effective SEO software created for link building, website analysis, rank tracking and competition analysis.