Right now at Monoprice you can save 20% off on orders up to $500. The promo code for the discount is Incentive.
The code is being sent out via their newsletter and is not unique. However, Monoprice has been asking people to forward the email with the code to verify the promo. Signing up for their newsletter is completely free and probably worthwhile in case they ask you for proof.
Monoprice ships from the US, so bare this in mind before making any orders. Duties & taxes will apply as usual.
The promo code expires December 31st, 2012.