Check out this huge bundle from CGSphere with over 8200 items featuring brushes and alphas for ZBrush.
The package includes 1850 brushes and 6400 alphas for creating highly realistic human characters, animals, environments, clothes, weapons, and more. The items suit both modern and historical visual styles, from Roman ornaments to jeans seams, and will help you make your scenes and characters more diverse and lifelike.
Blender artists can also use this full collection, with thousands of alphas available.