Online Money By Participating In Affiliate Marketing

This type of making money is accounted in CPA (Cost per Action) model. And action, in most cases, is defined as a sell.
That means you will earn money, when someone will buy product or order a service via your referral link or recommendation
Commissions may be very various, but most common is a percentage of the sale price. Standard is 5-10%, but for some products, commission is as high as 20-50%

Most profitable online niches are:

1. Financial products (mortgages, loans, bank accounts, bank deposits, Forex accounts)
2. Products related with making money online. It’s very wide niche. We can find here hosting providers (for example Hostgator or  Bluehost), tools for keyword research, like Market Samurai or Traffic Travis, or other plugins and tools related with this topic
3. Products and services for health and beauty (tutorials, diets, exercises, pills  etc.)
4. Products and services in tourism branch (hotel and fly reservations, trips, car rental services)

Below you can find 3 services, with a lot of affiliates programs for you:
Clickbank
Commision Junction
Amazon Associates