The sdl.com corporate website has an integration with Marketo. Here are some details from a functional point of view:
Marketo forms are presented on the Tridion webpage in an iframe. The form is created in Marketo, which results in a Marketo form url. With a manual action the Marketo form url is added to a Tridion form component. This component can be linked to an event page or a download page by users.
When the Marketo form url is introduced to the Tridion environment, the form component need to be published. The form will be presented on every event page or download page that is published.
When using an iframe to present the Marketo form, all form styling need to be applied in the Marketo form builder (I believe there is a 2.0 version), but it has limited styling options and form field functionality.
Translation / localization
Each form component holds one Marketo form url for a specific language. Supporting ten languages requires localization of the form fields and submit button and the creation of ten forms in Marketo. This will deliver ten Markto form urls. In Tridion the parent form component will be localized in all the local content publications. The local components will have the language specific Marketo form url. The result is that the Japanese download page will have the Japanese Marketo form presented in the iframe without additional handling by the user.