What I'm using right now is FreeMyApps, an iOS app (I think that it also exists for Android) that asks you to download other apps, giving you points to redeem through gift cards. At first it seems like it's a bit of a pain in the *** to have to download them all but, eh, it isn't that bad. At least you get something for it, like I have - I've got like $50 so far in Visa cards. You can sign up
here (mobile).
There's also Unbabel, a site which pays you to translate small portions of texts. You have to be fluent in at least one language and you'll need to do some tasks in order to get access to paid tasks. I've won over 90 dollars for this.
UserTesting is one of my faves. $10 for each video test you record - basically you have to use some site or app that they tell you to while recording your screen and yourself talking. There's not a lot of tasks all the time, but when you do get them, it's great...
Prolific Academic is my fave of them all. You have to answer to small surveys (and you instantly know if you're eligible or not), and you're told the reward you'll get for answering right away. Just the other day I was offered 5 pounds (7 dollars or such) for playing an app or something.

Join
here if you want to.
Even with limited time on my hands I manage to get $100 from these sites every month. It's great in case you have small things you want to buy... or even saving up for something.