What can you do with it?
– Create an AdSense account
– Manage an AdSense account
– Create and modify AdSense for content ad units and link units, AdSense for search boxes, and Referrals
– View detailed reports to monitor performance and earnings
You must apply to actually use the API and you will need quite a bit of page views before they will let you use it so don’t think you can start coding it all straight away. It will be interesting to see what tools, if any, come out of this API.
Blog Post here: http://adsense.blogspot.com/2006/05/introducing-adsense-api-beta.html
Apply here: http://services.google.com/ads_inquiry/api_application?sourceid=aso&subid=ww-en-et-asblog_2006-05-30&medium=et