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.

Comments:
SEbasic
11/24/2005 01:23 pm
This has been going on for a while now. At least the last fortnight or so - Lots of UI testing going on at Google it seems. Now the question is - it is well performing or badly performing ads that appear at the bottom of the SERP's?
Barry Schwartz
11/24/2005 01:33 pm
It has? I have never seen a thread on it. I'll take your word for it. But you do ask a good question. :)
Sergey Pasechinik
11/25/2005 08:52 am
I see it at the top of the results. It looks like they're still thinking about how to make it better. Sorry for my bad English.
Shawn Hogan
11/25/2005 08:43 pm
I've seen it myself in searches all this month. And Barry, if you haven't seen a thread about it, you've been looking in the wrong places. ;) <a href="http://forums.digitalpoint.com/showthread.php?t=36260">http://forums.digitalpoint.com/showthread.php?t=36260</a> (from about a month ago).