Knowledge is my stock in trade, and I use TiddlyWiki and Mind Mapping a lot.
Like all Wikis, TiddlyWiki is a great tool for capturing ideas and facts in text and linking them to other relevant topics. It's not so good at showing you the big picture.
Mind Maps (tm) are a great way of presenting the big picture, but programs like FreeMind and MindManager (tm) only show the notes for a single branch at a time.
What if you think of each tool as giving a different view on the same data? Then you could get the best of both worlds.
There's already a hypergraph extension for TiddlyWiki which allows you to see a visual representation of wiki contents but I prefer a more conventional Mind Map that I can edit.
I'm currently experimenting with a simple Python script which converts a TiddlyWiki into a FreeMind Mind Map. The converter works well for small wikis and I'm currently researching how best to structure larger maps.
The converter isn't ready for prime time yet, and documentation is minimal, but it's evolving fast. If you're interested please drop me a note ( at romilly dot cocking at gmail dot com) and I'll send you a copy.