Google has announced an interesting new feature in AdSense, Google-certified ad networks.
Ad networks are like the ad marketplaces where advertisers and publishers get together. Though the advertisers and publishers don't meet each other physically, the ad network works as the intermediary between these two parties who want to buy and sell advertising space.
Up until now, AdSense served only AdWords ads (except for some display ads from third party vendors). With this change, they are going to allow third party ad networks to serve ads to AdSense publishers. This feature will be initially made available to publishers in North America and Europe, but according to Google, will be rolled out to other regions in due cause.
This means that more advertisers will be competing for ad spaces and the additional competition is certainly good news for publishers.
For more information, see this post on the AdSense blog.