That depends what you mean by region. Considering large regions: The Alps. Largest ski area on one ski pass: Salzburg super ski card. Largest linked ski area: Les 3 vallées.
France. For more information see: "What is the world's largest ski resort?"
The largest unlinked ski area is of course the Alps. The largest unlinked ski area available on one ski pass is offered by the Tirol Snow Card giving access to more than 3000 km of piste in more than 70 ski resorts.
Whistler-Blackcomb.
There are many stores that sell ski equipment, all over the country. Depending on the area of the country, there is a specialized shop in your area. In the Washington area, you can visit Fairhaven Bike & Ski.
Ski Dubai is an indoor skiing resort in a mall in Dubai. A link to a map for Ski Dubai is under 'Related links' below this answer.
There is a massive indoor ski resort built on the desert sands in Dubai. Ski Dubai is claimed to be one of the largest indoor ski resorts in the world, with 22,500-square meters of indoor ski area.
Val Thorens is Europe's highest resort, also in the Three Valleys, the largest ski area in the world.
It is the largest indoor ski resort but it is not nearly as big as most outdoor ski resorts.
It is known for its great ski resort located in the commune of Saint-Bon Tarantaise which is in the French Alps. It is very famous because its is part of the largest ski area in the world named Les Trois Vallees.
The Meribel resort is part of the world's largest linked ski area. For those that don't ski there is also a ice skating rink, walking trails and a pool too!
The largest ski resort in France and in the world is Les 3 Vallées with 600 km of piste. For more information look at the question "What is the world's largest ski resort?"