I did a one month free trial with Audible.
When attempting to cancel, I was offered 50% off for three months if I stayed with them.
If someone else could verify that this works for them that would be great.
Thanks to Online Bathroomware:
You can stack the cancellation offer by selecting 'I get more credits than I can use' and you should be offered a $10 coupon. Then go ahead and select 'The membership fee was too expensive for me' to get the half price membership for three months.
I have done this before, and it was enough to keep me there for another 3 months. Good idea for a deal.