If you'd just like to see the email address entered by a given party...
1. Open your event.
2. Navigate to your 'RSVPs' tab.
3. Click the 'View All Details' link to the right of the party you wish to view the e-mail address of.
4. A lightbox will open showing that party's details, including the email address used to RSVP.
You can also export a list of all email addresses by going to your 'RSVPs' tab and clicking the 'Export to Spreadsheet' button.