During my high school days, I was a pretty decent golfer (about a 2-3 handicap, for you other golfers out there). I was asked by my local club professional if I would help him teach his junior golf clinics that summer. If you have specialized skill in any sport, there are definitely opportunities out there for teaching others the fundamentals (and getting paid).
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.