Plenty of options, but a slightly difficult interface.

My Take

Mindomo is a mindmapping tool, free to use, with plenty of flexibility. I've experimented with it a fair amount with the goal of using it for students to map projects and research and possibly even flowcharts for computer programs. However, I stopped short of using it in the classroom or even recommending it for students to use on their own. The interface is a bit confusing to use, requiring a fairly long time to create a document. The controls are not quite intuitive, and customizing the arrows and boxes takes too many steps. More effort to make the interface natural would greatly benefit.