FreeMind is an open source mind mapping software from Softonic that enables you to visualize ideas, projects, concepts, brainstorming, internet research or any other task that can benefit from a structured overview. You can create nodes with child and sibling nodes and add icons, clouds, notes and custom formatting for better presentation. The nodes can be expanded or collapsed, or interactively linked to local files, other maps, online resources and more. You can also insert encrypted nodes or create encrypted maps for sesitive projects. The finished maps can be exported to HTML, clickable XHTML, Open Office document, image file and other formats.

Vue 

VUE is a free, open source concept mapping application written in Java. The application is developed by the Academic Technology group at Tufts University. The Visual Understanding Environment (VUE) project at Tufts UIT Academic Technology is focused on creating flexible tools for managing and integrating digital resources in support of teaching, learning and research. VUE provides a flexible visual environment for structuring, presenting, and sharing digital information. VUE is licensed under the Educational Community License.

EDraw Soft 

Edraw Mind Map is the quick and easy map mapping software for creating great-looking mind maps (graphical representations of thought processes) for brainstorming, problem solving, rational analysis, and decision marking. It includes thousands of ready-made graphics that you simply stamp to create your drawing. Edraw Mind Map is a vector-based freeware with rich examples and templates. Easy to create basic flow charts, mind map, brainstorming diagram and sketch map.