I ran across another interesting option today called VUE.
-Vurbal
I think it's worth distinguishing between mind map applications on the one hand (Freeplane etc.), and concept mapping apps on the other (VUE etc.), although there is some overlap. The former are essentially hierarchical outliners (though laid out horizontally), where the process of development is hierarchical, flowing from a single, general central idea to many more specific sub-ideas.
Concept mappers on the other hand don't impose hierarchical thinking, rather, they let you connect any node to any other node in any particular order.
A third category might be programs that let you visualise the connected structure of your ideas that are implicit in your notes database. E.g. the
Navigator tool in ConnectedText.
I'm not suggesting that one category of these tools is better than the other. They serve different purposes. The main thing to decide is what status do you want to give to the conceptual tool of hierarchical ranking in the development of your ideas. Sometimes hierarchical thinking is helpful, at other times it's unhelpful. So it's more about choosing the right tool for the right job every time.
Another interesting concept mapper is
Cmap Tools (though I prefer to use VUE). There is also
Scapple, which integrates with Scrivener. For mind mapping, I use Freeplane, as I like its minimalistic approach, plus it's very easy to assign shortcuts to particular operations.