Dropbox Referral Program

https://dropboxreferralprogram.com/

Dropbox Referral Program is when you have a Dropbox Basic account, you'll earn 500 MB of space for each friend you refer to Dropbox. If you have a Dropbox Plus, Family, or Professional account, you'll earn 1 GB of space for each friend you refer to Dropbox. In total, Dropbox Basic accounts can earn up to 16 GB through referrals.

Free