If you enjoy writing there are many sites that you can make money writing articles. I personally have experience with Textbroker.com, but others include Associated Content, and Helium. For Textbroker.com you submit a writing sample to apply, which in return is graded to decide what you will be paid. From there you can pick from a list of articles that fit into your qualifications. The earning potential can be high if you write many articles, but if you are like me and only enjoying writing something that interests you, you may not make as much money.
Pros: If you enjoy writing, this is easy!
Cons: Writing opportunities go fast, pay is low.