For Citi cardholders only, Amazon
offers free 1-day shipping
on select items via coupon code "CITIFS13". (Eligible items are marked on the product page under the "Special Offers and Product Promotions" tab; you must select One-Day Shipping at checkout.) That's the best offer we've seen for Citi cardholders at Amazon since last winter, when we saw $10 off orders of $50 or more.