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.
Leadfeeder - Leadfeeder converts your website visitors into sales. Connect your website's Google Analytics to Leadfeeder and unlock the power of seeing who`s visiting your site!
Google Trends - Explore Google trending search topics with Google Trends.
Lead Forensics - B2B website analytics and lead generation.
Keywords Everywhere - Free browser add-on for keyword volume, CPC & competition
Clearbit - Clearbit provides Business Intelligence APIs