johnblack - 1:57 am on Jan 15, 2011 (gmt 0)
I've been following this thread all day and just thought I'd chip in with my 2c.
If I thought I'd exhausted all avenues re ad-placement etc, I'd turn my efforts towards improving my ranking in the SERPS to drive more traffic to the site.
I'd slap on Analytics and see which keywords give me a good return on Adsense and then optimize the site around them, whether that's new content or existing content. Of course if you rank #1 for those keywords then ....