Confluence - Confluence is content collaboration software that changes how modern teams work
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.
MS SharePoint - Share, organize, and discover information with Microsoft SharePoint. Learn about SharePoint Online, OneDrive for Business, and Apps for SharePoint
draw.io - Online diagramming application
Notion.so - A new tool that blends your everyday work apps into one. It's the all-in-one workspace for you and your team
yEd Graph Editor - yEd is a free desktop application to quickly create, import, edit, and automatically arrange diagrams. It runs on Windows, Mac OS X, and Unix/Linux.