AttackForge.com - AttackForge is the #1 Penetration Testing Management & Collaboration Platform for Enterprise. Bringing Security & Business Together On Your Pentesting Program.
draw.io - Online diagramming application
dradis - Dradis is the open-source reporting and collaboration tool for IT security professionals.
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.
Faraday IDE - Collaborative Penetration Test and Vulnerability Management Platform that increases transparency...
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.