For now, just log into your AdSense account, select the My Account Tab, then Account Settings. Under Account Settings select Ad Display Preference and you’ll see the dropdown for selecting a preferred Google Adsense font.

Google has opened up the possibility of choosing between Arial, Times and Verdana for one’s AdSense ads. That’s good progress. I think the standardized display is a weakness of AdSense/AdWords. It makes the ads less interesting. So this is a step in the right direction. Now they should also figure out a way for the advertiser to have a bigger influence on the formatting of the ad.

Check out the blog post here (thanks to Jonas Lejon for the tweet linking here):
http://www.searchenginejournal.com/google-adsense-lets-publishers-change-fonts/8714/