Serve, which is basically an Amex  pre-paid credit card, will offer virtual world cash rewards, redeemable in Zynga’s FarmVille game, for real world dollars charged. To kick off the promotion, you can Like the Facebook page for Serve and earn yourself a FarmVille tiger. What a tiger is doing on a farm is not explained, but I certainly hope there will be virtual deer and antelope for sale since those tigers need to be fed.

The deal, being announced today, will focus on FarmVille at first then expand to other Zynga games like CityVille and CastleVille.

According to All Things D:

First, FarmVille fans that visit the Serve farm will be prompted to plant a virtual Serve Money Tree on their farm. Then, they can register to receive a Zynga Serve co-branded prepaid card in the mail. Next, they’ll have to link the card to a bank account, debit card, credit card, or cash using a GreenDot MoneyPak.

And, once all the steps are completed, then they will be able to use the Serve card anywhere American Express is accepted.

And there you have it, money does grow on trees. Spend it as you please, which, I guess, means buy stuff for your virtual farm.