EVE Online. What can I say that hasn't already been said a million times. The game is the most unbridled sandbox ever devised in the framework of a game that facilitates one thing: War. Most of the game is played outside the game client through politics, diplomacy, and espionage. Running a corporation in EVE is A LOT like running a real business, and those that are good at networking and management in real life absolutely excel in EVE's environment. It's also a great place to further develop interpersonal and management skills along with blowing up spaceships that actually are gone when they burn to bits.
It's free to play now, so you have no excuse when it comes to giving it a whirl. People think you can't play EVE Online casually. This is dead wrong. If you can dedicate around 4 hours a month to the game, you can be a cute little NewBee Alpha Clone (alpha clones are the F2P players) that will be welcomed with open arms into the community, more specifically the Karmafleet corporation in the Goonswarm Federation alliance.
I am Londala Pox, and I am inviting you to dip your toe into the sea of EVE. Karmafleet has all kinds of resources (people, things, and space) to catapult you into the fun. Check out the game with this buddy invite (http://secure.eveonline.com/signup/?invc=6ee5bcf4-0a00-4ad0-a0f3-a9a19baeaddf&action=buddy) and apply to Karmafleet (https://recruit.karmafleet.org/) if you find it interesting. I would not say "find it fun" because the game is enormous, complicated, and at times obtuse. You will figure out how to have fun with it, and what you want to focus on, as you go. Come check it out!
**WARNING** EVE has just gone through a major change from an API platfrom to a ESI platform for third party utility integration. The current recruitment website for Karmafleet is under construction for the moment, but don't panic! You will need weeks to get your bearings in EVE, so hanging out in High Security Space until things are fixed will not hurt you in any way.
True, EVE Online is unique in the MMO world. It is brutal like life, the law of the stronger and the interests of different groups. I have been an EVE player for over three years and I consider this game to be brilliant. I do not recommend it to people who like action - this game is rather slow and is based on alliances, trickery, cunning and intelligence.
You can become a trader and sell ISK, you can join an alliance (corporation), you can become someone's vassal - you can become a miner and there are many more options.