Affiliate Programs are simply programs set up by the business owner for others to sign up for and promote for the business owner for a agreed upon commission (usually between 10 - 75%).
The great thing about Affiliate marketing is it doesn't cost you a single penny to get started, you don't have to worry about refunds or customer service that come with owning your own product.
All you have to worry about is generating the traffic to your affiliate link and collecting your commission checks.This is the quickest way to get started online... Period!
Here's a few Affiliate Directories to give you a start:
Associate Programs - http://www.associateprograms.com Refer It - http://www.refer-it.com