Some of the most popular ways that people are making money online is with adult sites, gambling and I know of one student who started a bulletin board and made enough money to put himself through college.
The fastest way to make money is to find out how others are making a lot of money and then do the same thing. The best way to make money is to take something you love and turn it into a business.
Google's Adsense seems to be a promising thing to do if you want to make money online. If you want to know more about Google Adsense you should read their message board - full of posts of people who have asked the question of can you really make money over the Internet. Google also has some examples of "success" stories about people who make a lot of money using adsense.