You guys beat me to it! As dazzlindonna mentioned, approved AdSense publishers can paste Google ads or an AdSense for search box on any page. However, you should first make sure the new site complies with program policies:
If you need help implementing the code, check out the FAQ entry pointed out by caspita.
After you paste the code to a new page, our crawlers will automatically detect your site and determine its content. Relevant ads should start to appear within several hours.