In the early days, gamers had to mostly pay for Massively Multiplayer Online Role Playing Games (MMORPG). But today some of the most popular MMO's are becoming free to compete with industry giant World of Warcraft.

Whether you want to be a superhero defending the innocent or a fantasy warrior slaying dragons, players will fine a variety of online options without paying a dime.

But these games do feature a catch, and developers have found a way to make money. Most of these games fall into the freemium Internet business model, giving players free content to play and lots of VIP features for players who are willing to cough up the extra cash.

Here is a list of the best free-to-play MMO's on the marketplace and the catches developers use to get players to pay for premium content.