I've heard a number of people wondering how to get mouse wheel working with DeepZoom images, unfortunately this doesn't work out of the box.

I've updated my mouse wheel sample from a little while back for Silverlight 2, the new version is really slick- Silverlight's DOM bridge is pretty powerful and I was able to do all of the browser hooks from managed code- no need for browser Javascript!

The updated project source can be found here and run from here.

Just the mouse wheel source is here.

The code to use to make a DeepZoom image zoom around the mouse:

Point lastMousePos = new Point();
double zoom = 1;

public Page() {
   InitializeComponent();

   this.MouseMove += delegate(object sender, MouseEventArgs e) {
       this.lastMousePos = e.GetPosition(this.ZoomImage);
   };

   new MouseWheelHelper(this).Moved += delegate(object sender, MouseWheelEventArgs e) {

       double zoom = this.zoom;
       if (e.Delta > 0)
           zoom *= 1.3;
       else
           zoom /= 1.3;

       Point logicalPoint = this.ZoomImage.ElementToLogicalPoint(this.lastMousePos);

       this.ZoomImage.ZoomAboutLogicalPoint(zoom, logicalPoint.X, logicalPoint.Y);
   };
}