I have posted a quick ZIP file containing a sample project that shows you how to use the output from the Deep Zoom Composer with Silverlight's MultiScaleImage control.
|Download Sample (Zip)|
Beyond giving you a working example, this implementation also includes a C# approach to getting mousewheel support in IE, Firefox, and Safari (Mac). You can read more about my mouse wheel support on my blog here.
For another example using the keyboard, please read Mike Taulty's post on this topic.
Update: Scott Hanselman has posted a modified version of this code with panning, click-to-zoom, and more! Check it out here.