If you like Google's Chromecast streaming HDMI dongle, especially its faster and more colorful second generation, here's something to keep in mind. If for whatever reason you've so far thought the Chromecast's $35 price to be way too much, you'll soon be able to get one for essentially $20 less. Starting on December 13 (and up until January 2), when you buy and activate a new Chromecast you'll receive $20 in Play Store credit for free. You can use the $20 to buy apps, games, movies, TV shows, books, basically everything that's up for sale in Google's marketplace. If you are a fan of paid stuff in the Play Store, then it means you've actually paid only $15 for the Chromecast. This deal has briefly appeared on the Chromecast Offers website. It's gone now, but that's probably because it was put there too early - we are in fact still a couple of days away from December 13. So it's a safe bet that if you go to that page from Sunday on, you'll see this back up. When you do (and if you bought a new Chromecast), just click the big blue Redeem button, and you'll receive the aforementioned Play Store credit. Alternatively, you can use the Offers section in the Chromecast app for Android to achieve the same...
Source: http://www.gsmarena.com/from_december_13_buy_a_35_chromecast_and_get_20_play_store_credit-news-15483.php