I found bubbl.us very easy to use. It was easy to navigate the tools and easy to share my finished product. It is free, which is a fabulous price. The downside, it is not very "fancy" and does not have images. Out of the three it is the least impressive, yet simplest to use.Mindmeister was also easy to use. It is free, but you only get three free mind

maps. You can delete the maps after you make them, so it is not entirely limiting. It is much prettier thanbubbl.us, but still does not have images. It shares the same enter and tab functionality (adding subtopics) as bubbl.us.
Webspiration looks and feels a lot like Kidspiration and Inspiration. This program was by far the most "advanced." It offers diagrams and outlines. The outlines are a nice added feature. It is a little more complicated to use mainly because of the added functionality. It has graphics and the ability to upload your own graphics.
view my map at: http://www.mywebspiration.com/view/378548a7215
I would use Webspiration in my classroom. I think that my kids would benefit from the graphical aspect of Webspiration. I could use it with my non-readers by having them mind-map using images rather than text. I love this use of nonliguistic representation!