At Grazitti Interactive (Marketo LunchPoint Partner), we have successfully integrated various technology platform with Marketo.
Here are few LaunchPoint links for our integration work:
Wordpress-MKTO plugin: http://launchpoint.marketo.com/grazitti-interactive/1312-wordpress-plugin-for-marketo/
Would be great, if we could hop on a call and discuss Shopify and Wordpress integration. Please suggest few time slots via email to fix a call.
M +1-650 417 9738 | E: firstname.lastname@example.org