Amazon is currently promoting their new Clothing Store Emails, and just for signing up you can get a free 20% off your next clothing purchase coupon. Just head over here to sign-up for the emails which will contain trend updates, special sales, and exclusive discounts. You should receive your coupon instantly via email after you sign-up. The coupon I received does not have an expiration date listed, so you may be able to hold onto it for a while.
For more info, head over here.