MyPoints! The referrals are done through email so just comment or email me with the email address you want to sign up with and I will have the site send you a referral email. You earn points by reading emails, filling out survey's and by shopping which you can redeem for gift certificates to stores and restaurants. It's really easy. I've been a member since June 2006 and I've earned over 16,000 points just from reading emails and filling out survey's.
bzzagent.com. Reply with your email and I'll send you an invite. You get to try products and services with samples, coupons and stuff like that. Then you share your opinion of the product and who you shared it with. You get points and can redeem them for stuff. I haven't redeemed any points yet, but the free products are worth it. I've gotten 4 coupons for free burgers at Chili's, coupons for Baskin Robbins and a Sonicare toothbrush (the kind with the charger and sanitizer) and that is worth way more than I would normally spend on a toothbrush.
You don't have to pay any money to join any of these sites.
These are all basic downline programs. You sign up and whenever you participate in the program, you get points/money and so do I.