According Darren Rowse (from Problogger.net) Google is secretly testing new Adsense format.

Here’s the scoop. Adsense are testing a system where by the publisher not only chooses from a number of prescribed ad formats (as we currently do) but where they themselves are able to determine: 1. the ad format size - 2. the number of ads to be shown in this space This is an interesting development because it allows publishers to have much greater control over the design of ads and the integration of them into their sites. It would give real freedom to publishers to find the very best position on their site without needing to completely rearrange their site’s design to accommodate them. There is no word of when such a system might actually go live but as far as I can see they are testing it in a number of places which could mean that it is sooner than later. Adsense Developing Fully Customizable Ads Blocks? Source: Darren Rowse (from Problogger.net)

(Via: Inside Google :