Makagiga is an open-source, easy-to-use, portable application for doing a variety of tasks, such as todo listing, text editing, or RSS reading. Plugins are used to implement its various capabilities.
Freeplane add-on for task management and memo taking
Freeplane is a widely used mind mapping tool. GTD is a time management methodology by David Allen.
Freeplane GTD is an addon, that can collect tasks specified in a mindmap, thus allowing the users of Freeplane to use the concepts of GTD in their mind