How can I see who has added a session to their personal schedule?

When attendees add sessions to their personal schedules in the event app, you can track those sign-ups by going to the Agenda module.  

The total number of people who have added the session to their schedule is listed on the right side of each session, and exporting the Agenda details spreadsheet will show you the specific attendees for each session.

The email addresses of each attendee who has signed up for the session will be listed under the Attendees column, separated by commas.