The Amazon Appstore hasn't exactly grown to rival Google Play in size or overall quality, but there's still some cool stuff over there. And if you can get it for free? That's a pretty good deal. Amazon is offering $5 to spend on apps and all you have to do is download something.
Starting on December 24th and running through the 28th, anyone who downloads an app or game using the latest version of the Amazon Appstore client will get a $5 credit to spend on Appstore content. It doesn't matter if you've had the Appstore installed before or not – just get the new version and you're good to go. The app you download to trigger the deal can be free – including the free app of the day, which Amazon is going to be pushing hard this week with big names like Angry Birds Star Wars II and Quell Memento.
The free Amazon money is only for use in the Appstore. You can use it to get paid apps and games, or to make in-app purchases.