You can get a free blog site at
http://www.blogger.com. Just write about a topic that interests you and join an affiliate program or two. Then put your affiliate links on your blog and advertise your blog. This is a really cheap and easy way to get started with affiliate marketing.
I have a website about internet phone service, and have just started a blog on this same topic. Both my site and my blog include links to some affiliate products that I promote.