Freebitcoin.io offers 50% referral commission for friends you bring who play the Free Bitcoin (BTC) game.
Invite your friends to join Dropbox, and for each one who installs Dropbox, you'll both get 500 MB of bonus space up to 16 GB.
Get lifetime referral bonuses through every new user you suggest. The bonus will be added into your account, every time they make a claim.