It’s been about nine months since Facebook rolled out its virtual currency, Facebook Credits.

Now the Internet social networking giant will make its Credits widely available in the physical world, by selling them on pre-paid gift cards available at Best Buy and FBCreditsWalMart stores in the United States.

No, you can’t use Facebook Credits to buy a six-pack of beer or a new iPod. The currency remains limited to use in the social games and applications popular on Facebook, where people can use Facebook Credits to buy virtual crops for planting in the Farmville game, for example.

Facebook began selling Facebook Credit gift cards at Target stores earlier this year, but landing on WalMart and Best Buy shelves should vastly expand the availability of its fledgling currency – at the end of 2009, WalMart had more than 3,600 stores in the United States.

Facebook won’t say what percentage of its more than 500 million users currently use Credits, though the company says the idea of selling Credits cards  in brick-and-mortar retail stores is to expand access to a broader group of people and to increase the use of Credits.