Some valuable tool you need to succeed in your SEO efforts.
Google Keyword Planner (Free): Help you evaluate the demand for your products and services. Also help you understand how people are searching for the services your are offering.
Google Trends (Free): Allows you to see trend for particular terms on the web.
Google Analytics (Free): Invaluable to understand your website traffic. You don’t need fancy expensive tools, this is all you need.