Hi James,
The adCenter Developer Blog has a post about API access: http://adcenterdev.spaces.live.com/blog/cns!40C96A663056EEA8!112.entry. This should help you get started.
There is also an API Forum here: http://forums.microsoft.com/MSDN/ShowForum.aspx?ForumID=901&SiteID=1
Hope this helps.
Thanks!
Carolyn