Google Opinion Rewards

This is one that most certainly falls into the ‘never going to make you much cash’ category, but for Android users it’s a bit of a no-brainer.

In short, once you’ve installed the app, it’ll pop up a survey every now and again. In exchange for answering a few questions – they’re never more than a few questions, and it tells you how many are in each survey – you get a small amount of credit added directly to your Google Play balance, where it can be redeemed across movies, games, apps and anything else for sale there.
The amount that you get is small, but each survey takes such a short time that filling it in is worthwhile, provided you’re happy sharing the data. It’s worth pointing out that not all the surveys have a payout, but the majority do.

Google Opinion Rewards [Android]