Right now all new US Kindle Fire owners can get 500 FREE Amazon Coins  from Amazon!
Coins can be used to purchase Kindle Fire apps, game, or in-app items!
100 coins are worth $1 so this is a $5 Value!
Since I was not familiar with the coins here is what I found online :
“E-commerce leviathan Amazon today is taking a step into social gaming: Amazon Coins, its new virtual currency, is now live in the U.S. To kick it off, Amazon announced that it would put $5 worth of the currency — equivalent to 500 Coins — into all Kindle Fire users’ accounts to use on apps and in-app purchases on its platform. The company says that this is equivalent to “tens of millions of dollars” worth of Amazon Coins.”
Check your e-mail if you are an “old” Kindle user. They probably already sent you an e-mail letting you know you received them.