Nigel Sampson brought
the Mouse Wheel into Blend as a Behaviour and you can drag it onto your control to get Mouse Wheel support.
One fairly useful piece of functionality missing from Silverlight is the use of the Mouse Wheel, thankfully there's a lot of code out there about how to use the Html Bridge to receive DOM events and bring in Mouse Wheel functionality.
The trouble is that with these examples you need to wire up all the events and manually deal with the mouse wheel. Silverlight / Blend Behaviors can help with this quite a bit by encapsulating all the required functionality in a simple drag and drop component.