Is there an easy way to export all the subject lines used in our various e-mails to a spreadsheet? I want to tie them to other data I've exported and determine which were the most effective.
No there is none. You would have to use the API to do this. See Get Emails » Marketo Developers
If you have Marketo RCE, you can use the Email Analysis report to do this.
Thanks, guys! Is there another way to do this without RCE or use of the API? We don't have RCE and using the API sounds like overkill just to pull this one data point.