You can find a list of affiliate programs and affiliate networks on thefreecountry.com's Affiliate Program page at URL thefreecountry.com/webmaster/affiliate.shtml

To join an affiliate network or program, simply go to the site and complete their online application form. Some programs will give you instant approval while others require a human to check out your application before it is approved. Once it is approved, you'll be given some HTML code which you can cut and paste into your web page. Note that some affiliate networks and programs will not accept you unless you have your own domain name. If you are planning to earn from your site, you should seriously consider registering your own domain name.