None of these lists are complete, as websites come and go and there are probably many more in each category here that I am unaware of. If there is one I have not included and you feel it should be, please let me know.
I am sorry, but I have not included any Diecast model links. They are generally not of any great interest to me – and there are already any number of sites with exhaustive lists on the Internet. The same applies to models in other scales as well.
ABC BrianzaItaly
ALMItaly
AMRFrance
Alef ModelsIsrael
Alfa Model 43Italy
André ModelsSweden
Arena ModelsItaly
AutodromeNetherlands
AutomodelliBrazil
Automodelli StudioAustralia
AutoparcoItaly
Axel'RFrance
Azzara Model AutoBelgium
BBRItaly
BMA43Netherlands
BRM Model CarsItaly
Bentley Classic ModelsUnited Kingdom
Big River ModelsAustralia
Christian Gouel (SLM 43)France
Competition43Germany
Creative Miniature AssociatesUSA
Crossway ModelsUnited Kingdom
DVA ModelsUnited States
De RoosNetherlands
Denizen MiniaturesUnited Kingdom
Derrez ModelsNetherlands
Eastern Models CollectionUkraine
Emmebi ModelsItaly
Faenza43Italy
FrancorchampsBelgium
GaffeFrance
Gamma Models (Klaxon, pinKo)Italy
Great American Dream MachinesUSA
Gulp ModelItaly
High Tech ModellGermany
HomburgmodellGermany
IV Model FactoryItaly
Ilario Carbone (Chromes, Contact)Italy
Inver ModelsUnited Kingdom
JMR43Switzerland
Jade MiniaturesFrance
Jimmy FlintstoneUnited States
John Shinton ModelsUnited Kingdom
K & R ReplicasUnited Kingdom
Kenna ModelsUnited Kingdom
Kit Car 43Spain
L'Eau RougeBelgium
Landsdowne Models (Brooklin)UK
Le Mans MiniaturesFrance
LookSmartItaly
MA CollectionSwitzerland
MA Scale ModelsUnited States
MG ModelItaly
MR CollectionItaly
Make Up Co., Ltd (Eidolon)Japan
MarpytoysNetherlands
MarqueartUnited Kingdom
Marsh ModelsUnited Kingdom
Meri KitsItaly
Midlantic (Illustra, Mini Marque)UK
MimodelsCanada
Mont Ventoux MontageFrance/Belgium
easter 43 miniaturesGermany
Neo Scale ModelsNetherlands
PE43-ModelleSwitzerland
Paddock MiniaturesFrance
Profil24France
Quarter MileUnited States
RaMei ModelleGermany
Racing DioramicsUnited States
Racing43Italy
RenaissanceFrance
ReplicarsNetherlands
Retro43Czech Republic
Rialto ModelsNetherlands
S & D ModelsUnited Kingdom
SMTSUnited Kingdom
Scala43Germany
Serge Divies ModelcarsFrance
ShowcaseAustria
Sprint43Switzerland
Studio27Japan
TRL ModelsChina
TecnomodelItaly
TenarivFrance
This Way UpSouth Africa
Tin WizardGermany
Top Model CollectionItaly
Touchwood ModelsUnited Kingdom
Tron ModelsItaly
Ugo Fadini (Omicron, Tom)Italy
Van DorenFrance
Vincenzo BosicaItaly
YoW ModelliniJapan
Z ModelJapan