I am a huge fan of XMind. I have my own personal license. However, I needed an alternative toolset for my new work laptop.
As I trolled www.lifehacker.com, I ran across an article about Coggle. Coggle is free, web-based and easy to use.
After about 5 minutes of getting familiar with the tool set; I was on my way of diagramming out my new solutions.
I recommended it as an alternative if you cannot get XMind or Mindjet.
Here is the link to the Coggle website. https://www.coggle.it