This page will lead you to several of my favorite hobby shopping sites. I will provide you my personal, totally biased and subjective reviews of these companies.
1. GreatModels - my current favorite. They aren't the cheapest but they have good selection and service and a nice web site. Greatmodels.com
2. Roll Models: what can I say about Roll Models. Love to hate them, hate to love them. But I have been buying from them since way back when they were called Battle Hobbies, before the Internet! They have an amazingly wide selection(but I suspect they don't really have most of the stuff they list, because...) THEY ARE SO SLOWWWWWWW!!!!!! I have waited three months for orders. I think they do a lot of re-selling, that is they don't have much in stock they just know where to find it. But they still have great prices!!! I am a patient sort so I don't mind too much the wait. Rollmodels.com
3. Squadron, of course very well known and big. no comments needed Squadron.com
4. Hobbylink Japan - "like having a friend in Tokyo" or something like that. Good selection and prices overall, but soooo far away! check out hlj.com
5. Discount Hobby Center, Ithica NY. No web site. Cheapest prices anywhere but just try getting ahold of them. NOT easy.
1. 48 Special Models - (Germany) very specialized 1/48 scale models and conversion kits, resin, mostly WWII German. 48specialmodels.com
2. Antares Models (Argentina) same as above - and really big on the Me262 variants!! Antaresmodels.com