Update: People are reporting getting their gift card about 2-3 weeks after signing up and getting their membership card.
This deal expires 09/01.
Originally posted on 06/27:
-Purchase a $55 Gold Star membership and get a $10 cash card by mail with promo code: JJBABYGS
-Purchase a $110 Executive membership and get a $20 cash card by mail with promo code: JJBABYEXEC
Executive members get a 2% rebate check based on their annual Costco purchases. If your rebate check is less than $55 you can take it to the Costco membership desk and they will refund the extra amount you paid for the executive membership.