While working on the Printing chapter of his Silverlight 4 Book, Pete Brown decided to build a simple report writer.
The book chapter goes into great detail on the printing API. I won't duplicate that here. However, you can find additional information on MSDN.
The goal of the report writer is to create a simple way to print reports in Silverlight. A non-goal was to create a report designer or similar. I'll leave that to you all and to the vendors.