A few weeks back I posted a new screencast about the Data Migration Manager in Microsoft Dynamics CRM 4.0 here:

Microsoft Dynamics CRM 4.0 : Data Migration Manager with John O'Donnell 

The product team have now posted sample data for Microsoft Dynamics CRM 4.0 which uses the Data Migration Manager, here are the links:

Microsoft Dynamics CRM 4.0 Sample Data (On-Premise Edition)

Microsoft Dynamics CRM 4.0 Sample Database Readme (On-Premise Edition)