XMind

With XMind you comfortably create mind maps under Mac OS X and collectively use them. The created topics of a mind map can, in addition to a classical mind map, be organized hierarchic, branched, as a table and more. The finished maps can be saved locally or shared with others over the free XMind Share Account.

Also Windows and Linux are supported by XMind, which makes it useful in businesses with a heterogene IT infrastructure.