As reported in February, Google will start to deliver video ads through Google Adsense this week.
"A certain segment of advertisers have told us that they want richer and more engaging messaging capability," said Gokul Rajaram, product management director of Google's AdSense program.
AP says that the ad will show an image that when clicked will start to play a video of up to two minutes.
Hopefully Google will not include the video ads in the same category as image ads to push them to a wide number of publisher that sticked with the default settings. They did this with animated ads, that were animated Gifs.
You can see an example at Google Adwords blog.