Unlike Firefox, the Opera Web Browser can be setup to block Google AdSense Ads without the addition of a plugin. Enabling Opera to block AdSense Advertisements is a simple process that can be done via it's Advanced preferences as explained in the following tutorial.
How to Make Opera Block AdSense Ads:
1. Launch Opera 2. From the Menu navigate to Tools-> Advanced-> Blocked content
3. Next, from the "Blocked content window", Click Add Type http://pagead2.googlesyndication.com/* and Click Close to apply the changes.
That's it, Enjoy browsing with your Ad-Free Opera Browser.