My school has been subscribing to http://www.mywebspiration.com/ for as long as I have been at the school.
Proven visual learning methods give students a framework to brainstorm ideas, gather and organize information, build comprehension, and develop written essays, papers and reports. Educator and student resources, including lesson plan ideas and study tips, support curriculum integration, and online access facilitates peer review, collaboration and student-teacher interaction – engaging students, extending learning time and increasing achievement across the curriculum.”
I was reminded that we had a subscription during a PD day last year. Unfortunately when I came to use it this year I found that the school no longer subscribed, as no-one was using it, despite the inservice training that was provided.
Ironically, now I could no longer use it I went looking for free alternatives and came across https://coggle.it/ a rather simplistic, though effective mindmapping tool. It offers far less than webspiration, but it is free and it very easy to use (busy with it after 2 minutes)
Freemind, on the other hand is a java program that you download. Its got many more features, a lot of little gimicky icons etc and is a mindmapping alternative that promises much, certainly from the internet entries I have read.
Neither match up with the collaborative features of webspiration. However, if your looking for a tool to encourage your students to map out concepts and content, and encourage reflection they are worth a look. They appear to be the leading free alternatives.
The following video will both try to sell you iMindmap and also give instruction as to how best create a mindmap