SE Ranking - All-in-One cloud-based SEO software for agencies, marketing teams and webmasters
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.
Yoast SEO - Yoast SEO does everything in its power to please both visitors and search engine spiders.
Google Trends - Explore Google trending search topics with Google Trends.
SEO-Hero.tech - SEO Hero is a free topic explorer. Find concepts related to your topics or Keywords and drive a strong content strategy for your website
Keywords Everywhere - Free browser add-on for keyword volume, CPC & competition