Wow... its really fun, you can literally make anything you want, sell it, script and drive it, whatever you can think of is pretty much possible if you make it.
Good things:
its only $10;
its a 17mb client you download, because everything is streamed off servers.;
lots of fun;
low lag;
BAD things:
you MUST have broadband to play;
scripting objects can be hard if you dont know anything about scripting languages;
driving isn't always too good.
if you want to own "virtual" land, then its a monthly fee, depending on how much you own.

the link is: www.secondlife.com
Things ive done since late March: built boats, started a drag racing association with a friend, crashed a "wedding"(i started sniping before i realized it was a wedding ), joined a Penguin Gang (we all wore penguin suits (kinda like mascots) and wreaked havoc on a mafia group) and a crap load more.

P.S.  if you decide to get this game, in the resident referal box when registering, please put my username in there: Super Penguin                , and please ask any questions!!!