Social games maker Zynga is launching a program that will give AT&T customers access to exclusive games and content as well as a number of other perks.

AT&T customers will receive free credits for Zynga’s games, which include Words with Friends and the smash hit FarmVille. Zynga players typically have to buy credits for Zynga games with real-world money. Those credits help players advance in Zynga games more quickly than players who don’t buy Zynga credits and also give them access to exclusive items and content.

It’s Zynga’s first deal with a wireless provider. AT&T was the first carrier for the iPhone, which now features most of Zynga’s online games and is a huge part of Zynga’s mobile strategy. Zynga apps will appear on AT&T’s main site of the Android Marketplace, giving them preferential display over other Android Marketplace apps.

Zynga’s latest social game, Empires and Allies, is another hit for the company. It attracted more players than Farmville, its first breakout hit, in just 25 days. Empires and Allies is gaining new users at a rate of a million a day and 8 million a week, according to AppData.

The company has become a Facebook distribution powerhouse like no other game company. That makes it a lot easier for Zynga to generate revenue, since a percentage of users usually pays for items in otherwise free games. The company has delivered hit after hit to Facebook, including FarmVille and CityVille.

There were reports on Tuesday that Zynga might file for an initial public offering as early as Wednesday in order to raise up to $2 billion. Those reports indicate Zynga has a valuation somewhere between $15 billion and $20 billion. That would put the company’s market value well ahead of massive game publisher Electronic Arts, which currently has a market cap of $7.5 billion. Activision-Blizzard, which typically caters to console and hardcore gamers, has a market cap of around $13.3 billion.