In the past I have found mind mapping software an effective tool both personally and with students. For example, a couple of years ago I completed a sequence of lectures that would feed into an exam with a 30 minute exercise where I encouraged each student to form their own mind map of the content that had been covered. Not only did this enable them to identify and revise the module contents but it also provided a tool they could use in their revision planning.
I looked for an app to allow me to generate mindmaps on the iPad. and found 'Simplemind' to do what I was looking for. It has a simple functionality - easy to use. The free version allows the generation and storage of mind maps - fine for use in the classroom. Buying the full version (£2.49) allows the maps to be disseminated through email or pictures.