Google AdSense has begun contacting publishers about participating in a new beta test which would see publishers running rich media advertising instead of the standard text and graphic ads. Their rich media offerings include interstitials, expanding ads and floating ads.
While expanding and floating ads would be expected in rich media advertising, interstitials is an interesting choice by Google to include in this beta test. Interstitials are ads which are displayed as a full page ad before the user is redirected to the webpage they expected to see.
For more details and how this beta test could impact other rich media companies, there is a detailed entry on JenSense.