The peer-to-peer concept is coming to virtually every corner of human existence. That includes the hospitality industry. Through AirBnB you can actually rent out your house for various lengths of time for a predetermined fee. That gives you an extra income on your house and gives the visitor the benefit of having an entire house, rather than being crammed into a single hotel room.
One of the cool things about Google AdSense is that it's so easy to get set up. If you have a blog or website, you can sign up for a free Google AdSense Account. From there, Google will give you a unique code that you will paste onto your website. Google takes it from there, tracking your page views, traffic, and earnings on your behalf. There is no upkeep or maintenance to get this thing going, which makes it a no-brainer if you have a website already.