That is right, Jeff Martin, over at Search Engine Watch Forums found Google testing Google AdWords ads, right under the listings in the Google results. He named the thread Google running ads beneath SERP results now - Very Yahooish and posted screen captures. He is the screen capture of the adwords at the bottom of the results.
The search looks to be on click fraud detection, but it must be one of those geo tests, because I do not see the ads.
Forum discussion at Search Engine Watch Forums.