Getting involved with affiliate programs is a great way to start earning income online. Affiliate programs consist of special links on your site that point back to an internet marketer's site. If a visitor to your web page clicks on the link and/or (depending on the program) purchases something through the affiliate link on your site, you receive a small commission. While the per transaction fee is usually quite low, it is possible to start seriously making money online with affiliate programs if you can get a large audience to come to your website and click on the links. Many companies allow internet users to start making money online by advertising their goods and/or services. The most prominent affiliate program is that of the online bookseller Amazon.com.
Start a blog - Blogs are very popular. If you have an interesting topic and you can keep people coming back for more you can make a nice living with your blog. The way you would make money is through programs such as google adsense or adbrite. You can also sell products or services on your blog. You can start a blog for free with blogger or wordpress.
Writing articles - There are several revenue sharing sites that share their revenue with their writers. They will place google ads around your articles and when someone clicks you get a percentage. Most sites pay 50%. Some pay less and some pay more. A few great revenue sharing sites are ehow, triond, flixya, helium and associated content. If you write enough articles you can make a decent side income.