Funny you should post this! LOL! I just joined Second Life (
www.secondlife.com) which you can create your own character/body, and they say you can make real money there too. They now allow a basic account for FREE (where you can just explore, interact, build objects, etc.) You have to pay $10/mo to create a premium account to own land and then a monthly land fee on top of it if you do own land. But you get a weekly allowence either way. Though it's in their own currency and to convert it to real dollars, it's like I think 250 of their dollars to $1 US. Or something like that. But just going here and there and exploring can be fun.
They also let you create scripts and objects and run them. Plus you can even sell them too. These scripts can do nearly anything. In fact, some of their staff and advisors gave me some that may be usable towards building an AI car!
The 3D is pretty good and the Help land I am in the graphics/world is pretty neat. I haven't been to the main land. You have to grab all the "freebies" you can off the help island, do all the tutorials, ask questions, practice, etc. first and take notes on a notebook if you want. Because if you go off the help island, you can't return. It's for newbies only. Once you leave you can't go back. But you can stay as long as you'd like I think, to learn what you want. And there's staff there to talk to and help. Also on the main land you also can get staff to help you anyway. They also have a WIKI, forum and stuff on their web site.
The whole world requires a download of a speical client to run and view the world, interact, etc.
It's not too hard to learn. The help island tutorials were easy to get through, people were friendly and helpful, and we even had an impromptu disco dance on New Year's Eve, complete with a campfire in the middle of the blinking squares. LOL! You see the darndest things go on there, let me tell you! LOL!
I also visited Disney's Virtual Magic Kingdom:
http://vmk.disney.go.com/vmk/en_US/index?name=VMKHomePageA long-time friend of mine is a HUGE Disney fan and he showed me around. VERY limited as it's for kids, and you can't always type what you want to say. But still fun and interesting.
Of the two, I'd obviously recommend Second Life. Plus SL does have some special "adult" or "mature" areas there as well, for those so inclined. Though you are amply warned that they are such areas so you don't run into one by surprise, I'm told.
I'm going to explore SL in some of my free time.