Does the wordpress e-commerce plugin has the authorize.net payment gateway?
There are several plugins available that support Authorize.net, however, they don't all support the same interfaces. Authorize.net provides the following APIs
SIM = Simple Integration Method
AIM = Advanced Integration Method
ARB = Automated Recurring Billing
CIM = Customer Information Manager
All but the first require that you also install a secure certificate on your site to encrypt communication of credit card or check details. The first option, SIM, sends the user to Authorize.net's site to complete the payment, so it's on their secure connection.
CIM isn't likely to be supported in a plugin since it's for more advanced ecommerce functions and wordpress wouldn't be a fit for them anyway.
There are some free options that you can find in the directory: http://wordpress.org/extend/plugins/search.php?q=ecommerce
You can also choose a commercial option, such as this:
http://simplecreditcardpayments.com/ /shaglevoojio
Here are details about how to get SSL on your wordpress blog to support Authorize.net http://www.youtube.com/watch?v=8F8iPxs4naY /omegle
