SharePoint Server 2007

SharePoint Server 2007 SDK: Software Development 

http://www.microsoft.com/en-us/download/details.aspx?id=79

BDC - Business Data Catalog

http://msdn.microsoft.com/en-us/library/ms563661(v=office.12).aspx

Register SharePoint list as a BDC application

http://social.msdn.microsoft.com/Forums/en/sharepointbdc/thread/e5fece49-ef8e-4da9-a58e-1b43545444f9

How to create a BDC Entity Association using SharePoint SDK Applicatoin Definition Designer

http://social.msdn.microsoft.com/Forums/pl/sharepointbdc/thread/8d0b7dc8-85a9-496f-9f5a-490e49cb80b9

Content Sources Overview

http://msdn.microsoft.com/en-us/library/ms545416(v=office.12).aspx