I believe the textbook way, at least with the old Traffic Cop implementation, was to create a field on the Contact/Lead objects for "Nurture Track" - you can then run a report off of this field in SFDC. For each nurture track, be sure to add a "Change Data Value" flow step to toggle this field.
New school way might be to create an Engagement Program which syncs to a SFDC Campaign. You can even go a level deeper and create different campaign member statuses and progression flows if your sales team needs details. The campaign object can be a related list on the Contact object, which'll show nurture track status to your sales team.
You can use both methods in conjunction for best results.
I have a field "Nurture Program". This shows the current nurture program a lead is in (I have chosen that a lead can only be in 1 program at a time). I could create SFDC campaigns as well, but I would have to filter out marketing nurture leads (not MQL yet), as these should not be in Salesforce yet. Syncing a Marketo program to Salesforce will result in every member to be synced to Salesforce automatically.
We utilize SFDC campaigns. Every nurture campaign has a corresponding SFDC campaign. Anyone in SFDC in that nurture campaign is tagged with that SFDC campaign. If someone syncs to SFDC later on we have a back end workflow that will add tha appropiate SFDC campaigns to their history.