Keyword Discovery - Keyword Discovery is a keyword research and analysis tool.
Keyword Surfer - Get search volumes & keyword data directly in Google.
SheerSEO - SheerSEO helps you to track Google Search Engine Rankings for critical keywords. PageRank, Back Links and more.
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.
GrepWords - Grepwords is an API-first Google Keyword Suggestion Tool.
Keyword Tool & Content Assistant - Content optimization tool to boost your rankings