American Flyer S-Scale trains were manufactured by the A, C. Gilbert Co. of New Haven, CT between 1946 and 1967. They continue on today manufactured by Lionel. A large segment of S-Scale involves the collecting and operating of vintage A. C. Gilbert American Flyer and whatever is available from other manufacturers today. Those hobbyists who like to operate AF as well as collect it often have highrail layouts. AF made many neat operating accessories which gave the AF layout lots of action and even a personality as Mike & Ike, Gabe the Lamplighter and Smitty the walking brakeman did their chores. Lionel now manufactures AF and has produced a ton of new items the last few years.
Now is a great time to be into S gauge model railroading. MTH has been producing operating accessories like the ones Gilbert used to make. K-Line is now making many items of AF/compatible rolling stock with engines and train sets coming in 2005. Lionel has been and is continuing to expand their AF line with a brand new Mikado leading the way.
There are many S gaugers who have the best of both worlds by allowing for both AF trains and scale models being produced currently by S scale manufacturers. They model what is known in S gauge circles as Hi-rail. This is the fastest growing portion of S scale.
When they coined the phrase "Model Railroading is Fun", they must have had American Flyer in mind.