SalesOptimize - Selling to online retailers? Revolutionary sales lead generation search engine driven by deep web analytics
Clearbit - Clearbit provides Business Intelligence APIs
Rescan.io - Find the technology stack behind any website. Get the lists of websites using any technology.
ZoomInfo - ZoomInfo is a B2B database providing detailed business information on people and companies.
Elucify - A completely free software tool that uses crowdsourced data to find business email addresses
InsideView - InsideView aggregates and curates all the company and contact data, news and social insights, and professional connections you need to do business better.