Who is on the bus? You are, if you want to be. Anyone following a bus link is "on the bus".
When do they go to the bus stops? Whenever they get bored with the wiki they're at.
What do they do there? Follow the links to the next stop.
Is the bus even active? In as much as the wikis involved have not died, and their bus stops have not been vandalized, yes.
I'm new to wiki.
Well, you've come to a good place if you're interested in what wikis there are on the web; the TourBusStop should lead to many interesting communities. If you're interested in this wiki in particular, take a look at our HowTo for how it works, or have a look at some of our StartingPoints.