There are sites where you can copy and paste the same posts from your blog and get credit to your Google Adsense account. Just register your publisher number and add your posts.
These are some of the sites I use:
Senserely Yours http://www.senserely.com/referral/77777b6b
Blogger Party http://bloggerparty.com/referral/626d4001
Dollar Space http://www.dollarspace.net/signup/&friend=gabesmom