Confluence - Confluence is content collaboration software that changes how modern teams work
draw.io - Online diagramming application
Slack - A messaging app for teams who see through the Earth!
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.
Yammer - Yammer is a leading enterprise social network used by more than 200,000 companies worldwide, including 85% of the Fortune 500, to get work done smarter and faster. Sign Up Today.
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.