Many people already know Adsense, which is a Google advertising service. Google Adsense has many good points:
Any sites, even the smallest, can signup and use Adsense on their pages
You just have to copy and paste a code on your blog and then wait for money
Google can send you a cheque or they can send money to your bank account directly, which is good for non-US residents
Google Adsense has its bad points as well:
That's three good points as well as three bad points. You have nothing to lose and Adsense is easy to integrate. If you're looking to make money online, this is definitely a solution to consider, especially for a small or young blog.