There's AdSweep at http://adsweep.org/ http://adsweep.org/ - I've never managed to get it to work on Opera 10 under Ubuntu, but I find it works well on Chrome a

There's AdSweep at http://adsweep.org/ http://adsweep.org/ - I've never managed to get it to work on Opera 10 under Ubuntu, but I find it works well on Chrome and plenty of people have given it good reviews.