Here in Philadelphia we actually still have several lines which run, though it'd be quite nice if they restored the ones they promised to bring back when they shut them down a 15 years ago.. But, yes, they are a good thing and it's good that more cities are bringing them back.
Philly trolley map. Green and light green still run. Red ones suspended in 1992. Blue ones killed in the 80s. Black are the two subway/El lines, and the yellow and pink are high speed trolley-like vehicles.
(ht brendan)
...for comparison, a 1932 trolley map.
