Click Bank has a great program, and some make a living off this.  The below is copied directly from their site - they say it best. 

ClickBank affiliates are Internet marketers who earn commissions by promoting ClickBank products. Once you sign up as an affiliate, your internet marketing skills can lead to additional income.

Here are just a few of the features and benefits over 100,000 affiliates just can't stop talking about:

  • Simple, fast, and free account setup.
  • Over 10,000 products to promote.
  • Commissions as high as 75%.
  • High-converting products drive high ROI on your marketing programs.
  • Reliable and accurate tracking gives you credit for your successful marketing strategies.
  • We manage the publisher relationships, so you always get paid what you are owed.
  • Target new markets with phase one of Platform Globalization, which includes Spanish language products and a currency converter.
  • Since our first day of business in 1998, we've never missed a payment.

ClickBank makes it easy to become a successful affiliate. Opening an account and gaining access to our marketplace will provide opportunities you can't afford to miss. Just follow these simple steps and start earning right away:

Please note: as with all third parties, Clickbank reserves the right to change their policies and procedures at any time without notice, so make sure you check with them frequently.

A great third party company that has some excellent tools to advertise Click Bank Products is CBProAds.com.