Not to be left behind by its major rivals announcing big investments and acquisitions last week, social games developer Zynga revealed that it picked up $15.18 million in a new round of funding that attracted previous backers.

Combined with Zynga's previous financing rounds, which brought in $29 million last July and $10 million in January, the FarmVille developer has so far raised $54.1 million in venture capital. Participants for this third round include Foundry Group, Kleiner Perkins, LinkedIn founder Reid Hoffman. amd Zynga execs Mark Vranesh, Vishal Makhijani, and Reggie Davis.

The funding news follows just two weeks after controversy surrounded Zynga over its scam-like "Cost Per Action offers" advertised with its apps. The company vowed to rid its games of any misleading promotions, but they popped up again in its recently launched FishVille, provoking Facebook to temporarily suspend the aquarium simulator.

Zynga then announced it would remove all CPA offers, including legitimate ones from companies like Amazon and Netflix, until it could control and specify which ads appear with its games. FishVille has also since reappeared on Facebook, where it's picked 8.3 million new users in the past week, but that hasn't stopped at least one law firm from investigating a possible class action lawsuit.

The developer's new capital is the latest in a month filled with big news from major players in the social games space -- Electronic Arts announced a $300 acquisition of Playfish (Pet Society) a few days ago, and soon afterwards Mafia Wars developer Playdom raised $43 million, which it spent on purchasing Green Patch Inc. and Trippert Labs.