Through 2/6, pay only $1.99 (including a FREE stamp for mailing) for Valentine's Cards at Cardstore when you use coupon code CAA5187. You need to place your order by 11:59 ET on 2/6 to not only use the promo code, but to also get the card out in time for Valentine's Day.
Please note: when you click the link, the site will show a promo code to get cards for $2.49, but use the coupon code listed here (CAA5187) to get them for $1.49 with a FREE stamp.
You can also still get school Valentine's cards (which come in sheets of 4 cards per sheet) for only $0.99 when you use coupon code CCA5115 (through 2/6).
You enter the promo code on the billing page at checkout, and you'll see the discount reflected before you enter your payment information.