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.
SEMRush - All-in-one Marketing Toolkit for digital marketing professionals.
Google Trends - Explore Google trending search topics with Google Trends.
Moz - Backed by industry-leading data and the largest community of SEOs on the planet, Moz builds tools that make inbound marketing easy.
Keywords Everywhere - Free browser add-on for keyword volume, CPC & competition
SEOquake - SEOquake provides a browser extension to conduct on-page SEO audit.