While Eventbrite has a great integration with Salesforce.com, it would be great if there was an integration with Marketo directly so all the tracking can be more easily retained.
I would like to throw in that we would be interested in this integration as well. We bring in a lot of new leads/opportunities through our paid & non paid events and this would be super valuable.
Ideally Eventbrite leads go into Marketo first but until that happens Zapier is a good workaround. Pricing starts out at $15/month for up to 3,000 records.