Now Adsense allows HTTPS sites.
Google has announced that now Adsense publishers can monetize their HTTPS websites. Today many e-commerce websites and especially social networks like Twitter or Facebook use protected HTTPS protocol.
HTTPS sites must have all contents on the page be SSL-compliant. To use HTTPS adsense you justneed to create an ad unit and then paste the HTML code in your source code where you want the ad to appear.
Maybe in near future we will see Adsense on Twitter or Facebook? Lol