Virtual currency continues to expand into new territories.  This time onto your local store shelves.  Zynga announced on Thursday its users can now buy pre-paid game cards at several reatilers across the nation.

An astounding 12,800 stores that is.  Let's say you want to go buy a gallon of milk at 7-Eleven - well you'll find a Zynga card for sale there now.  Other stores carrying the social gaming startup's cards include Best Buy, GameStop and Target.  

If you're not all that familar with Zynga, the company is leading the way in the social gaming revolution.  It's created some very popular games including FarmVille, Mafia Wars, YoVille, and Zynga Poker, just naming a few, which all run on top of Facebook and MySpace.  Today, the San Francisco-based startup is seeing 67 million users playing its games on a daily basis.  

Social gaming companies like Zynga, pretty much make their money off either advertisements, or selling virtual goods and currency.  In Zynga's case, virtual currency can be redeemed for items like tractors or new seeds for the ultra-popular Farmville game.

The addition of selling physical gift cards to its business model will only help its virtual currency business model.  It gives those users without credit cards or bank accounts, like kids, the ability to now buy in-game items, opening a whole new breed of customers for the company.

Vish Makhijani, SVP at Zynga commented, “By partnering with 7-Eleven, Best Buy, GameStop and Target, our games can be accessed by a broader audience of new and existing players.”

So how much can you spend on one of these cards?  The company said cards would be sold at either $10 or $25.  

Back in December of 2009, Zynga raised $180 million from Digital Sky Technologies, the same firm which invested in Facebook.  Zynga continues to grow and now sees 235 million monthly active users.  Last month, the startup opened its first international office in India.  

Mark Pincus, CEO of Zynga delivered a great keynote speech at our last Vator Splash event, check it out here.  And check out details for our next Vator Splash event here.