Google has added more controls to blocking ads across your AdSense account. You can now differentiate the blocking of types of ads by site level.
Google said this will satisfy one of the "top requests" that they "hear from publishers who manage multiple websites." This come in handy when you want to block a type of ad from showing on your children focused content site but allow that ad on maybe a more adult oriented web site.
To make this happen, Google has added two new things:
(1) Site management: You create a list of sites you own under the 'Home' tab, visit the 'Account Settings' page and navigate to the 'Access and authorization' section.
(2) Site-level blocking: After you set up step one then you can click on the 'Allow and block ads' tab and then select the site from the left navigation and make the necessary updates. Here is a picture:
Forum discussion at WebmasterWorld.