The Chart Gadget lets you easily embed charts and diagrams into Google Wave using Google Chart API.

To use the gadget, select "Add gadget by URL" from the Edit toolbar in Wave. Then, enter the following URL: http://everybodywave.appspot.com/gadget/chart.xml.

Alternatively, use the installer XML at: http://everybodywave.appspot.com/gadget/chartxt.xml.

Short screencast at: http://www.youtube.com/watch?v=82xL7JzFVO8