Spicynodes is a visualization service that allows you to create nodes of information, links, text, photos, and other media and then link the nodes together in a way that makes sense. It can be used for mind maps, organizational charts, and even lesson plans.
There is a free version and I found it easy to use and set up. I liken it to a combination of Prezi and a mindmap. It's not a presentation, but it could be. It's not a mindmap, but it could be. It is a very versatile tool that can be very useful for educators and students.