Clickbank is one of the most popular affiliate marketing program that deals with digital products such as eBooks. This website has been around for many years and is among the first affiliate websites on the internet. Another great thing about this site is that it lets all people from different occupations to sign up for a free account. Once you sign up for the account, you will have an access to millions of eBooks that other members are selling. The quality of many of the items within the Clickbank affiliate program is debatable. But, the commissions are far and above many of the others on this list and much of the reason it is rated highly within this article is history and ease of use.
The topic you choose must have enough depth that you can create a lot of content for it. This is important for building an authoritative site, for search engine optimization, and most importantly, for the end user. If you don't have enough content about a topic, you're not going to be taken very seriously as an authority on the topic and it's unlikely you can convince someone to make a purchase from you.