SpiderFoot - Open source intelligence (OSINT) automation tool.
LibreX - Framework and javascript free privacy respecting meta search engine
sn0int - sn0int is a semi-automatic OSINT framework and package manager
SearXNG - SearXNG is a free internet metasearch engine which aggregates results from various search services and databases. Users are neither tracked nor profiled.
Maltego - Maltego is an open source intelligence and forensics application.
Sherlock - Sherlock provides insights on user engagement for product makers.