Alongside being a common link building method, guest writing on other blogs can also be a good way to generate income. If you're writing a lot of content on your blog you'll have a perfect portfolio to showcase to other blog owners that could potentially pay you to write for them.

Advantages: Not only can you generate some income from freelance writing, but you can also build links to your blog in the process as well as generating direct traffic to some of your other articles.

Overall, it's a fairly easy monetization technique to get started with and it can be very flexible in terms of time/resources.

Disadvantages: This is another question of resources. Although you can pick and choose your jobs, many blog owners will want you to commit to a certain number of posts to be written within a given time-frame.

If you don't have a lot of extra time for writing then this might not be for you.