Here is one that I like a lot and relatively unknown. Train Buddy. The shop is in Wake Forest, NC and Kim Parker is very knowledgeable, helpful and has great service. He has a lot of HO and N scale stuff in stock and has access to many major suppliers.
I placed a rather large order for 180 pieces of code 83 Atlas flex track and 58 various turnouts and all but 3 wye switches were ready for pickup within a week.
The three wye turnouts are on back order, they are Walther’s brand turnouts expected to be available in mid August.
I purchase almost all my MR stuff online. The following is a list of the ones I like the best:
http://www.wholesaletrains.com/Default.htmhttp://www.discounttrainsonline.com/http://www.trainsetsonly.com/http://www.traintrack.net/http://www.internethobbies.com/index.htmlhttp://www.tonystrains.com/http://www.firsthobby.com/store1/default.asphttp://www.modeltrainstuff.com/Wholesale trains seems to have the best prices but sometimes they don’t always have what I want in stock so I go to one of the otheres.
One place to stay away from ishttp://www.internettrains.com/merchant2/I have only had problems from them.