ClickBank - Selling your own product? ClickBank can enable you to accept credit cards with no monthly fee!

Commission Junction - Just starting out and don't have your own product yet? No problem. Commission Junction has over 1000 merchants who will pay you to promote their product for them.

FineClicks - Earn revenue with you website and newsletters using FineClicks.com.

Shareasale - Affiliate network providing multiple pay-per-sale, pay-per-lead, and pay-per-click programs for webmasters.