Geoff Webber-Cross, one of my most excellent Silverlight and SharePoint alumni, has just started a blog and published a neat extension to the Silverlight 4 Toolkit to implement chart zooming and panning.
The Silverlight 4 Toolkit comes with a chart control of its own. There’s a demo that shows how to pan and scroll the chart control, but the axes scroll with your chart, which is usually not what you want.
Geoff’s example shows how to overcome this and also gives you zooming into the bargain.