First of all
1. If you don't have a Google wave account, get one here
yourBrainStormer is an extension which will help you in your brain storming sessions.
This gadget allows users to share ideas across more efficiently during brainstorming session. The interface is intuitive and easy to use. Hint boxes will be displayed to guide new users on how to use this gadget. User will be able to view the description on each node by clicking once on the node. Users can choose to print the data. Animation Changes in the gadget will be accompanied with a simple animation.
Read more and get the gadget here
To Use
1. Open a wave, Click on Add gadget button
2. Enter the Gadget XML url
3. Click add