(Updated Oct 3, this is still on valid.) Right now Discover has a referral program where you can refer a friend to sign up for the Discover it credit card and both you and the new cardholder will get $50 cashback after they make their first purchase within 3 months.
Here is my referral link if you’re interested.
Discover it is a fairly simple card, with 5% rotating categories and their shopping referral program always give great cashback. Here is my last review of the card if you want more details.