Just found an interesting article on SAP implementation from Wikipedia. I guess it has been around for while already, but it has some interesting points which are generic for any ERP project.
Actually this reminds me that there would be a great need to make a sample ERP implementation project plan for free downloading. This could help creating project plans. Maybe somebody has done this already?
For the SAP users, http://help.sap.com provides some great resources for implementation planning.