Here are the most viewed adCenter API topics on MSDN for September 2009.
Microsoft adCenter API Version 6
Microsoft adCenter API Release Notes
Microsoft adCenter API Programming Reference
Microsoft adCenter Campaign Management API Reference
Campaign Management Service Operations
AdGroup Data Object
Campaign Management Data Objects
What's New in the SDK for the Microsoft adCenter API
Developing with the Microsoft adCenter API
Also, remember that adCenter API Version 5.1 sunsets on October 31. Ensure that you migrate to adCenter API V6 by October 31 if you haven't already done so.
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