Included in the latest release is the option for   ecommerce account holders to setup an affiliate program. Using this   feature the merchant can setup a commission rate to be earned by the   affiliates and banners for the affiliates to display on their websites.   Orders created by visitors who reach the site via these banners will be   tracked and an affiliate payment will be computed. The merchant can  keep  track of their affiliate payments via their website admin.
How it works:
The merchant creates an affiliate program with a   percentage based commission via the affiliates area in the Store   section. They setup an affiliate commission rate and write up how the   affiliate program works in the program description area. Then they add   banners that the affiliates will have to choose from to display on their   website.
Affiliates are created via the User accounts   system. This can be done via the normal user account to a group methods:   manually enter the affiliate user, create a form that sets up the   submission as a user in the group, the standard create account option
Once the affiliate user is created, the affiliate   logs in via the My account area and clicks the affiliate tab. They can   see details of the affiliate program and grab HTML to display the   merchant's banner on the affiliate website. Sales completed by customers   who reach the site by clicking the banner will be tracked and   commissions will be applied to the affiliate.
The merchant can view the amount owed to the   affiliate and register a payment by finding the user in the user   accounts area (affiliate group) and clicking the affiliate tab. The   merchant would still need to actually send the payment to the affiliate.