Before we go into the earning list you need to know that, making living through online requires a bit interest, desire and determination. I always recommend people to choose online earning money opportunities according to there hobbies and natural abilities.
1) Article Posting; this is a type of online earning which require some writing abilities. The writing can be of any criteria, but remember, writing about what you know and what you're much interested in is the best.
This is a money opportunity that has brought a serious flow of income to many people around the web. So, if you can gist about something why not put a pen on the paper and start writing about it? It is just easy as anything. Many article posting site are welcoming you. Unless you don't like or enjoy writing, you may choose the next one.
2) Simple Affiliate Marketing; This is the most popular way of earning money online. But the reason I made it as a second choice is that, many people have heard about it but still only few out of many are making some reasonable income. It involves selling company's products in order to get some amount of the sells cost. This amount is known as "commission". Many people fail because of one reason - they don't know how to get buyers. And as a result, they miss the flavour of affiliate marketing. But it is still easy to make a quick residual income, because it is faster than article posting. You may check my affiliate guide for beginners (it'll open in a new tab) so you won't get lost in the wilderness of affiliate marketing failure.
3) PPA: Paid-Per-Action; it is an easy to earn money online opportunity. And you know the more easier the less income. But don't get discouraged because the people who understand this, are making more money than expected.
As the name implies, PPA involves doing things to get paid. It may be playing games, commenting, carrying some simple task, uploading and many many interesting hobbies to earn you money.