Apache Tomcat - An open source software implementation of the Java Servlet and JavaServer Pages technologies
draw.io - Online diagramming application
nginx - A high performance free open source web server powering busiest sites on the Internet.
LucidChart - LucidChart is the missing link in online productivity suites. LucidChart allows users to create, collaborate on, and publish attractive flowcharts and other diagrams from a web browser.
vCenter Server - IaaS platform for managing and deploying virtual machines
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.