Audible is having a 20% off credits for subscribers, expiring on the 17th of July. Also, there is a 3 for 2 offer with 100+ Non-fiction books to choose from, expiring 14th of July. The books are from these categories:
Bios & Memoirs, Nonfiction, Science & Technology, History, Business & Self Dev.
Note: You may need to have 2 or less credits on your account to get the 20% off credits offer.
Also there is currently a free thriller book available called The Two by Will Carver I'm not sure if it's only available on US accounts or if Aussie accounts can get it too.
http://www.audible.com/pd?asin=B008DKGG02