I just found out about a really simple website for generating affiliate income, although it will work best if you're a publisher, e.g. a blog, magazine or information resource. Skimlinks provides a clever bit of code that automatically inserts affiliate links into your content, so you can make money if someone clicks through.
You just write your content as normal, and when people use your website they'll automatically see links straight to the recommended shop or website. To be fair, you'll need to get a lot of visitors and clicks to earn a decent amount of money from affiliate advertising, but at least it's simple. Clever!