Resource: www.clickbank.com

Notice the ads on the right side of the site? Yes, that's an advertisement of ClickBank. Shopping online is very common nowadays, and so one of the common tool for shopping online is using Clickbank. You can either be the Seller of the product, or the promoter of it. For promoting the product, you will earn certain % of commission if the consumer buy the product through you link. You can also choose what type of product to promote, hence making them relevant to your website. 

How It work: Firstly, go to clickbank.com and setup an account. After that, choose what kind of product to sell by going to "Marketplace" You can also make use of the "Hopadbuilder" to auto generate some product by entering keywords. All transaction is done by paypal.