Sorry, no longer available. Plum District, a daily-deals site, is offering a nice gift today for its users: Refer 6 friends to Plum District and receive a $40 Zappos gift certificate. To participate, just sign up with Plum District, then get 6 friends to do the same using your unique referral link. They do not have to buy anything from Plum District to qualify as a referral, but they do have to confirm their e-mail address after signing up. After your 6 friends have signed up, you’ll get a unique gift certificate code to use on Zappos for shoes, clothing, accessories and more.

Quantities of this reward are limited, so sign up now and start referring if you want to participate.