In the last few days i have seen on forums and blogs that people found a new type of Google Adsense Leaderboards. The Leaderboards seem to include link ads, that once clicked on, they show different ads.
Google seem to have integrated the link ads into Leaderboards to be more effective, but until now they stated nothing about it. We only have some screenshots and the word of people that saw the ads.
via DigitalPoint

August 13th, 2007 at 11:28 am
Interesting indeed.
I’ve heard many praise the link ads, and say they have a quite good CTR. Maybe Google has noticed this too and try to optimize the ad space better. I wonder if they will make a public statement about this soon.
August 28th, 2007 at 3:09 am
Your are Great. And so is your site! Awesome content. Good job guys!
August 28th, 2007 at 10:18 am
Thank you!
September 4th, 2007 at 8:35 pm
I think its a good idea. Havn’t seen it on my site yet. Lets see how it turns out, as they are only testing it on some sites.
November 27th, 2007 at 12:45 am
anything new is welcome as long as it does not affect our earning in an negative way.