Next Bus has the TTC streetcar system up in a beta version on their site.

http://www.nextbus.com/predictor/publicMap.shtml?a=ttc&r=501

That link will take you to a display of the Queen car, although as I write this, no service appears to be running west of Humber Loop.  You can select other routes from a menu provided on the page.  Right now there is no Carlton service west of Bathurst or east of Broadview, Dundas cars are all east of Ossington.  Data for St. Clair is reported only for the streetcar portion east of Bathurst.

This is a trial.  Don’t complain to me if it doesn’t work.  That’s what trials are for.  Apparently there are still cars with no GPS units, and this causes problems.  Of course it is possible that the service really is that screwed up, but one quick cross-check is to compare the number of cars shown on the display with the number of runs that should be in service.  For example, the Bathurst route shows only two cars even though four are supposed to be in service at this hour.

The site requires that you have Java installed to use the live map feature.