The best Mindmapping software? | educational technology for teachers |

I have been working to find the BEST mindmapping software.  Qualities I am looking for?  Free, detailed, flexible, printable, saveable and sendable.....Love Gliffy the most, but too much $$$.  I have used Creaza, but you can only store 3 maps for free.  I found mind42 confusing and hard to navigate.  So I think I am going to try to have my students work with LucidChart.  I have applied for a free educational account and will see if they get back to me.  So far it has everything I want/need.