Whether you're playing FarmVille, FishVille, or PetVille, you probably use Facebook Credits. As Facebook continues to grow beyond its 500 million users, so does the number of services offered on the site, which means growth for credits, too. Facebook on Thursday announced it is expanding this program to include more payment options and access for more developers.

"Our goal with Facebook Credits is to give people that use Facebook an easy, convenient, and trusted way to buy premium items in games and applications, while creating unique opportunities for developers to build successful, sustainable business," George Lee, a product manager for Facebook Credits, wrote in a blog post.

A new partnership with monetization service PlaySpan will offer more than 20 new payment options. Facebook Credits started testing in May 2009 and was launched in beta in February of this year. In July, Facebook teamed up with MOL Global to provide users in Asia with an easier way to take advantage of the Credits program.

Credits can be purchased through Paypal, mobile payment, gift cards available at Target stores, and credit card. Soon, PlaySpan will help Facebook offer payment options beyond this, within different games and apps. More than 200 games that include 75 different developers currently utilize this system. That comes down to 22 out of 25 of the most played games on the site, according to Forbes.

The post also said that demand from developers to join the credits program is high, and Facebook's expansion hopes to alleviate this.

"We're now able to add more developers to the program more rapidly," Lee wrote. "Our goal still remains the same: to enable you to focus on creating innovative games and applications while Facebook takes care of procession payments, dealing with fraud and adding new payment methods."