There is some news on the AdSense blog.

AdSense is introducing expandable ads.
In response to a click they can grow to use more of the screen.
They can also play videos.
http://adsense.blogspot.com/2009/03/introducing-expandable-ads-on-adsense.html

AdSense can also now serve third party ads.
http://adsense.blogspot.com/2008/05/introducing-third-party-ads-on-google.html

Washington Post story:
http://www.washingtonpost.com/wp-dyn/content/article/2009/03/05/AR2009030501709_pf.html

paidcontent.org story:
http://www.paidcontent.org/entry/419-google-deploys-ads-in-news-results-shutters-shared-stuff-bookmarking-se