Over the years I have participated in various rewards programs. Here are a few I love:
Disney Movie Rewards Points. Basically, you enter a code from a Disney Movie you purchase and watch them add up. Later you can use them in exchange for rewards like Disney merchandise or even gift cards! Many freebie websites will also post bonus points occasionally and sometimes there are promos where you can earn extra points by watching shows on tv and playing online video games.
Pampers Rewards. The main way you will find points is by purchasing Pampers diapers and such. The code will be on a sticker inside the package. Enter them online and when you get a bunch, redeem the points to get rewards. Again, freebie sites will often post bonus codes.
Recyclebank. Now you might be thinking, my town doesn't participate in their recycling program. Mine doesn't either. BUT you can still earn points to earn rewards. There are always tons of daily pledges, surveys, quick videos, and more. I primarily use this to earn free magazine subscriptions, but I have also gotten gift cards and free admission to children's museums, etc.