Google has officially entered the mobile advertising space by launching Google AdWords Mobile Image Advertising.
The service is currently available to interested advertisers who are targeting the following countries: Australia, Austria, Belgium, Canada, China, Denmark, Finland, France, Germany, Greece, India, Ireland, Italy, Japan, Korea, the Netherlands, Norway, Poland, Russia, Singapore, South Africa, Spain, Sweden, Switzerland, Taiwan, the United Kingdom, and the United States.
To get started to display mobile ads you will need to update your AdSense code. The supported banner sizes come in four dimensions: 305×64, 215×34, 192×53, and 167×30 pixels and acceptable file formats: .gif, .jpg, .png.
Here is a demo video by Sanjay Agarwal of Google: