NextBus Unites with Google Maps!
If you live in many cities, the transit systems are using a system called NextBus to tell you almost exactly when the next bus will arrive at a particular stop and help you avoid the fate of waiting for the train when it's pouring rain out for hours on end.
Using a combination of wireless transmitters and GPS, they are accurate, because they can account for traffic delays that a schedule can't predict. In the case of the N-Judah it's usually some guy double parking his car on the narrow streets in Cole Valley.
Now, NextBus is providing complete, accurate route maps and real time indicators of where all buses or streetcars are online, on a Google Map. Take a look and see for yourself at this link, which shows the N-Judah line, in real time.
Although not all SF Muni buses have NextBus installed at bus stops, this is a good start. It beats relying on the folks at Transit.511.org, better known as 511 Is A Joke, who are notorious for giving out info that's just plain wrong. You're better off calling SF Muni directly and asking directions if you're lost - 511 is a Joke almost always screws up.