Keyword Discovery - Keyword Discovery is a keyword research and analysis tool.
KeywordTool.io - KeywordTool.io is the best FREE alternative to Google Keyword Planner and Ubersuggest. It uses Google's autocomplete feature to get over 750+ long-tail keywords for any given query.
GrepWords - Grepwords is an API-first Google Keyword Suggestion Tool.
Keyword Lookup - Keyword Lookup is an innovative chrome extension that can provide you monthly Search Volume of keywords.
SheerSEO - SheerSEO helps you to track Google Search Engine Rankings for critical keywords. PageRank, Back Links and more.
Keyword Surfer - Get search volumes & keyword data directly in Google.