You could previously set salesforce.com tasks for prospects in completion actions for various objects like forms, form handlers, landing pages and more. You can now create and assign salesforce.com tasks right from within a Pardot drip program.
A salesforce.com task will only be created if the record is set to be synced into the CRM. Remember that by default, net new prospects do not get pushed into the CRM until they are assigned. For more information, please see our help article on When are leads synced with the CRM?