GM’s day is here on Drivethru RPG. There are several companies that have their goods on sale during this time.
Arid Hills Gaming : Sci-fi tiles
Dicey Ventures Studios – 6mm Terrain : Great for Battletech
Dicey Ventures Studios – Fantasy : All sorts of fantasy terrain.
Hobgoblin-3D : Fantasy Bundles. They also have single pieces on sale.
Rocket Pig Games : Wide assortment of terrain and miniatures.
Xerbath : Buildings and ships.
Via Ludibunda : Several building bundles and even a gallows.