Oren Gal has improved the Silverlight app he developed last year for Esri developer summit and added save/restore, selecting favorite sessions, and printing functionality.
Source: Oren Gal's GIS Website
So far, I have avoided dealing with printing in Silverlight, but no more. Read some articles and got to work. It took me 3-4 hours to complete it and I am pretty satisfied with the result.
The three steps of Silverlight printing are:
Step1 : Acknowledge that you have to build your page brick by brick.
Step2 : Design the page.
Step3 : Use the PrintDocument class.