You can signup for TripAlertz here and you’ll start off with $25 in free credit (And thanks for allowing me to refer you!)
Once signed up click here to get a link to refer your friends. For every friend who sign up you’ll get a $5 in credit.
Your friend only needs to signup to get the credit, they don’t need need to buy anything. Credits expire after 6 months.
With the credit you can book free hotel stays around the world that rotate weekly.