It really depends on the type of business you are opperating and the background you bring. Companies that operate content businesses or busineses that rely on advertising as their primary revenue model rely on SEO more than most others.<p>Regardless of the value you see in SEO, it drives a number of critical skills. SEO relys on data, keyword data, traffic data, bailout data, conversion data etc. and so learning about what makes SEO successful means you must have quality analytics in place and learn how to use them and that will make all of the operating parts of your business better and or more efficient.<p>Again depending on your needs and the size of your business SEO is best managed internally, rely on an experienced and reputable consultant if you need help.<p>Sites like SEOmoz and SEObook offer excellent information and tool sets to get you started for a minimal monthly fee.
I'm doing SEO myself as a consultant so it's very important for my business ;-) and I have to disappoint you:<p>1. SEO is not about "a tool", it relies on a plethora of factors and tasks many of which user solost has already outlined in his comment<p>2. There is no single tool that will allow you to do SEO work, you need a few tools, I'd say more or less 10 depending on what you actually do.
Three weeks ago I compiled a list of the most important ones:
<a href="http://www.seoptimise.com/blog/2009/07/the-30-free-seo-tools-you-must-know.html" rel="nofollow">http://www.seoptimise.com/blog/2009/07/the-30-free-seo-tools...</a><p>Nowadays SEO is more about "killer" content creation, social media and viral marketing than anything else. The basic on site SEO work and link building is trivial and not enough.