For new members only, Groupon offers an Audible 2-Month Trial Membership for free. (Living Social charges the same.) That's tied with our mention from last month, a savings of $30, and the lowest price we could find. This trial gives you a free audiobook download for each month. (You can keep the audiobooks after your trial.)
Be sure to cancel your membership before the trial ends to avoid a recurring $14.95 monthly charge.