Chums was (it's not active anymore) a website and mobile application to help friends find and recommend new products and services. It was offering features similar to Invitation codes (this site) and had a small following.
Chums was a small community of friends finding and sharing referral codes.
If you are looking for a place to promote your referral codes and share them with your friend, Invitation is definitely the best way nowadays.
It's time to get your Invitation.codes account too 😎