XMind has switched from proprietary commerical software to free software (freeware)!
Not only does it do mind maps but you can include spreadsheets, fishbone diagrams, tree charts, and org-charts. It works on Windows, Mac, & Linux.
It also has "Social Brainstorming" features that allow you to share, collaborate, and publish your mind maps.
Sign up for an account, download the free software, and then you can upload your maps.
See the EdVibes Screencast demo we made
Also check out XMind Tutorial