My favorite Google Wave gadget is MindMap gadget
I use Mind map on a day to day basis when I need to structure a topic, especially in brainstorming phase.
For this, I use freemind which an open source dekstop application.
I've discovered last week a gadget for Google wave that allow you to build a mind map within a wave.
Very powerful to work remotely.
Of course this first version has limited functionalities, but it's ok to start to use it.
All the informations are on "Bruce's blog"
Zemanta helped me add links & pictures to this email. It can do it for you too.