Just received this email today:
Special offer for Father's Day - Buy One Get One Free!
A personalised card from Hallmark is a great way to make dad smile this Father's Day. Choose from hundreds of Hallmark designs, and add your own message, name or photo to make the perfect card. We have cards for Dad, Grandad, Husband, and even cards to Daddy from the little ones.
SPECIAL OFFER: if you order before midnight Sunday 22 August you can buy one card, and get one free! Just use the voucher code BOGOF10 on the checkout page to get your free card. Cards are only $5.95 including postage. Offer can be used once per customer.
That's pretty good considering :
a) cards normally cost that much in the shop anyway
b) you can get it posted directly to them
c) you can personalise it
d) you get 2.. great if your Mum has married twice (and you still talk to both of them) :P