Overture's long-standing Ambassador program for search engine marketing firms is now allowing interactive and traditional ad agencies to participate. More details from ClickZ in Overture, Google Reach Out to Agencies.
The program provides participants with greater support in reselling Overture's products. It does not provide a commission on sales. The ClickZ article also covers how Google says it trying to do more to educate agencies about search marketing.
The issue of commissions came up earlier this year in our forums: Agency Commission Or Discount Offered On Search Ads? The nasty rumor was agencies were being given a commission by the search companies while SEM firms were not. Both Overture and Google eventually told me that at least in the US, they aren't offering commission payments to anyone.