Soovle - Soovle is a customizable search engine provides the search suggestion of the best provider on the net.
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.
Google Trends - Explore Google trending search topics with Google Trends.
iSpionage - AdWords competitor keywords with the click of a button and monitor competitor PPC landing pages.