I've only recently downloaded XMind, but so far it looks like another good mindmapping option. You can find out more about it, and download it yourself, from the XMind website.

There is a free version, and a "Pro" (subscription) version, and both include an online account to allow sharing of your mindmaps with other users. It appears the most significant differences in the two version include additional file export options and a presentation mode in the Pro version. You can see the full feature comparison here: XMind - XMind Pro.