The following are links to Colorado rail and Brill Trolley Sites:
Platt River, CO
Historic museum using one diesel-electric Gomaco Replica running along Platte
Fort Collins, CO
Historic museum running one restored 1919 single truck Birney Trolley on grass covered track bed aside main street.
Detroit, MI
Using 9 cars, seven from Portugal on in-street narrow gauge.  The first in street narrow gauge historic trolley system in the U.S. Their trolleys are JG Brill trolleys similar to No. 23  and Aspen's former trolleys.
Old Pueblo, AZ
They received two of Aspen's trolleys and are restoring No.524 and converting it to standard gauge.
Issaquah, WA
They received two of Aspen's trolleys, but yet have to install a 3rd rail to run narrow gauge.

There is much you can find out about historic trolleys on the Internet: 
Heritage Trolley
The Heritage Trolley site has links to all existing and proposed historic trolley sites.
Railway Preservation
This site has links to all existing and proposed historic trolley sites.
Railway Age
Here one can find many reports and links to associations, research organizations, and many reports on the benefits of rail transportation.
Historic Railway
This site links to Historic Railway Restoration.  Be sure to look at the Prior Project  restoring J. G. Brill #101, the trolley is similar to No. 23 and was re-engineered to use batteries for power. 
Gomaco
Gomaco is a leading supplier of refurbished, restored, and replica trolleys.Glenwood Railroad Museum
Glenwood Springs Railroad Museum operating in the historic Glenwood Railroad Station, dedicated to preserving rail and its history in the Roaring Fork Valley.