Moz - Backed by industry-leading data and the largest community of SEOs on the planet, Moz builds tools that make inbound marketing easy.
Ubersuggest - Want more traffic? Ubersuggest shows you how to win the game of SEO. Just type in a domain or a keyword to get started.
SEO PowerSuite - Get all SEO tools in one pack - download free edition of SEO PowerSuite and get top 10 rankings for your site on Google and other search engines!
Keyword Explorer by Moz - Find the best keywords to improve your website's SEO traffic
SEO Tools Centre - SEO Tools Centre provides SEO checker services for websites.
Keyword Surfer - Get search volumes & keyword data directly in Google.