1. Affiliate Marketing
Affiliate Marketing is simply promoting other people's products to earn a commission. When you sign-up for an affiliate product, you're given a special link to promote that product. Anyone that buys that product through your link will earn you a commission. You could easily create a simple WordPress blog that has a few reviews promoting a product on Clickbank.com or any other affiliate network. You'd then get the blog to show up in Google for those specific keywords that people are searching for, the visitor would then view your blog, and then click your affiliate link to purchase the product.

2. Kindle Book Marketing
3. Information Products