Here are a selection of links you might find useful.
European Model Shops
Scograil – Competitively priced supplier of European N scale. Based in Ipswich, UK.
DM Toys – Huge range of European N scale direct from Germany.
Menzels Lokschuppen – Huge range and some interesting products not carried by other suppliers. Definitely worth a visit if you are ever in Düsseldorf. Based in central Düsseldorf, Germany.
Modellbahn – Kramm – Huge range of products from a wide range of suppliers. Good prices. Well worth a visit and if you are staying in Düsseldorf as a DüsseldorfCard will allow you to travel out to Hilden on the S-Bahn. Based just outside Düsseldorf in a town called Hilden, Germany.
Contikits – Useful site for sourcing some older and second-hand European N scale. Based in Ryton, UK.
North American Model Shops
Model Junction – Great little model shop for North American N scale. It’s been a while since I visited but still gets good reviews so it can’t have changed much. Primarily online but you can visit the unit they operate from in Slough, UK.
Wig Wag Trains – My favourite online store for North American N scale when I lived in the States. Based in New Mexico, USA.
Eurolokshop – My favourite online store for European N scale when I lived in the States. Used to have an awesome sale around Thanksgiving but often cheaper than similar suppliers in Europe at other times of year; just don’t forget to factor in taxes and exchange rates if ordering from outside the US. Based in New York, USA.
Shapeways – Commonly used 3D printing service and marketplace.
Free-Mon – The official US web site for N scale free-mo modular railroading.
FreeMo N-RE – A European N scale modular standard.
Bend Track – The homepage of the Bend Track modular system.
T-Trak – A fun looking modular standard for small prototypes such as trams.
RailPictures.net – Photo galleries with a North American focus but does have some European content and contributors.
BahnBilder.de – Photo galleries with a European focus.
Rail Fan Europe – Photos of European rolling stock.
Flickr – You can find some interesting galleries and groups on Flickr such as this one that specializes in photographs of European tank cars.
RM Web – Interesting forum with sections dedicated to UK finescale N (2mm), 3D printing, scratchbuilding and European and North American railways.
1zu160 Blog – Useful site for seeing the latest N scale releases from large and small European manufacturers.