Honestly, I dont know why people always look for wordpress plugins, it is not that difficult to add the adsense code in the template files of any wordpress theme in seconds. a tip: use the text urls with 4 or 5 keywords close to the "this post was added to the CATEGORY" line below your posts for example...
So whats the best theme? GOSH. You can make ANY theme good if the overall design is being liked by your target group and you place the ads in the spots as mentioned above on the posts. The adsense "hot spot" guide on their official site is valid for wordpress blogs as well as any other site:
look here:
https://www.google.com/adsense/suppo...y?answer=17954
And there are two philosophies with your sites and blogs:
1. blend the ads into the theme so it looks more editorial then advertisy
(be careful not to violate the rules for placing ads near pictures etc.)
2. INTERRUPT your design with adsense blogs with formats that people are
not used to to avoid that they are "blending them out" while browsing at your site
(so both concepts are actually the extreme oposites!)
IMPORTANT: your wordpress blog needs to have a PRIVACY DISCLOSURE
as per the new adsense rules. The Script that I use (see my signature) has
already an automated privacy disclosure page build in and in fact I combine
that script along with wordpress blogs on the same domain.
Contact me for examples etc.