I love using Shopkick to earn gift cards to Starbucks and Target. It just takes a few seconds to check-in to stores like Target, Macy's, Sony, and American Eagle.
I mostly just use it to check-in, but sometimes I'll hunt Target and scan items for extra kicks. I've even gotten my mom and husband addicted to the app as well. And honestly, the fact that my husband is willing to use it should be quite the endorsement - he is not at all interested in most of the apps I use for rewards.
Do you use Shopkick? How much have you earned?