We are just going into beta on a plugin that integrates nopCommerce with Zapier.com which webhooks to various online email marketing platforms like MailChimp and Constant Contact.
For more information, see here
http://store.bluesphereinc.com/nopconnectand here:
https://zapier.com/zapbook/apps/#sort=popular&filter=email-marketingIf you are interested in getting the product for free and taking part in the beta, inbox me and I will get you set up.
Thanks,
Chris