To allow prospects to schedule time to talk with our Account Managers, we use an app called TimeTrade. The TimeTrade app creates a field on the User record in SFDC with the unique link for that User/Record Owner for their calendar, allowing prospects to use that link to book time with them.
Is there a way I can access this field as a token for a Marketo email or landing page?
You would need to write the field value from the User to a customer field on the lead/contact, and then use the token for that custom field. I don't believe there is currently a way to use fields from the User object any other way.