I’m 100% sure you must have heard about Facebook. And 80% sure that you have at least an account on Facebook. Facebook is the largest social and membership site around the web. You can get group of people in any niche you need. SO, it is the largest site to promote anything you need.
Many people earn money by creating and promoting Facebook page. It is an easy way to make money from Facebook.
Another way, you can add a Facebook like button on your website. Google is now giving much importance on social signal for ranking. So, if you can gather enough likes, it will promote your website on search engines. Along with, visitors will be influenced when they find that many people like your website.