Like the little engine that could, the National Capital Trolley Museum is a survivor that you just want to root for. The NCTM has lost a number of its streetcars through fires and an accident. More recently, there were rumors that the controversial ICC would lead to the demise of the NCTM. Fortunately, with its future move to new facilities, the NCTM will not only survive but be better than even before.
National Capital Trolley Museum
I've spent many an afternoon with my kids here, enjoying the scale model, peeping into the maintenance barn, and of course enjoying the ride on the 1.5 mile track in one of their many streetcars. The NCTM usually has a different streetcar out depending on the day.
HTM 1329 from The Hague
Run entirely by volunteers, the NCTM is a true diamond in the rough and well worth the visit. Check out their website for more information.