Google Sites is a powerful component within Google Apps. As a platform for document and information sharing and collaboration, most organizations see Google Sites as a means to provide Intranets, project sites, and secure customer portals.
Google Sites, however, can be made public. Some businesses (including Google) use this capability for open information portals.
Taking public and open the next steps, Google has integrated AdSense and Google Sites. If you have an AdSense accounts, you can now place ads and monetize their Google Sites.