Free-to-play online gaming is coming to the PlayStation 3. Free Realms, a massively multiplayer virtual world game that launched on the PC two years ago, is making its debut on Sony’s PlayStation Network on March 29.

The launch shows that the free-to-play business model — where users play a game for free and pay real money for virtual goods — is catching on with in the console world.

Sony Online Entertainment, the division of Sony that makes MMOs, previously published DC Universe Online on the PlayStation Network. But Free Realms, which has 17 million registered players on the PC and Mac, is the first free-to-play MMO to be slated for the PS 3’s online network. With two major MMOs coming to the PS 3, Sony is trying to differentiate its platform from Microsoft’s Xbox 360, which has no such MMOs on tap.

John Smedley, president of Sony Online Entertainment, said that Free Realms continues to break new ground in the game industry. Sony is pushing retail sales of DC Universe Online at the same time it is embracing the free-to-play business model with Free Realms. Free Realms is a fantasy-role-playing world that competes with the likes of World of Warcraft or Lord of the Rings Online, but its content is lighter and it is geared toward a younger audience.

The world is pretty diverse. You can train as a ninja, play soccer, battle pirate ships, cook a meal, enter a demolition derby, mine for gold, pursue a quest, and train exotic pets. You can socialize with friends, play mini-games, go on adventures and share your achievements.

Sony promises you can get into Free Realms quickly and easily from the PlayStation Store. You can create a character and jump into the world within minutes. There are 15 types of careers to choose and more than 30,000 combinations of clothing. The free-to-play business model got another boost with game maker Gazillion announcing today it would shift to that model.

Sony also has the Sodium free-to-play game in its Home virtual world on the PlayStation Network, but Sodium isn’t an MMO and is more like an arcade game.