Freeplane began as a fork of the Freemind project. While maintaining comparability with Freemind file format, it has far outpaced in features and development. As of 3/5/2022, the latest Freeplane update (1.9.3) is 3/5/2022 vs Freemind was last updated (1.0.1) 2/5/2016. Active, helpful community.
Xmind - Xmind is a brainstorming and mind mapping application.
draw.io - Online diagramming application
FreeMind - FreeMind is a premier free mind-mapping software written in Java.
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.
vym - VYM (View Your Mind) is a tool to generate and manipulate maps which show your thoughts.
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.