Extending Commerce Server Order System

http://blogs.msdn.com/sathishcg/archive/2006/11/08/extending-commerce-server-order-system.aspx
Extending Commerce Server Order System

Orders Example: Extending the LineItem Class, CS2007
http://msdn.microsoft.com/en-us/library/bb219308(v=cs.70).aspx
http://msdn.microsoft.com/en-us/library/aa544655(v=cs.70).aspx

Orders Extensibility Samples, CS2009

http://msdn.microsoft.com/en-us/library/dd451452(v=cs.90).aspx

Orders Example: Extending the LineItem Class, CS2009

http://msdn.microsoft.com/en-us/library/dd328349(v=cs.90).aspx

Orders Example: Adding Virtual Gift Certificates, CS2009

http://msdn.microsoft.com/en-us/library/dd452317(v=cs.90).aspx