Toolshed & Wood working shop
This is either one large building or a pair of smaller ones located next to each other and is very likely located in the courtyard area. Though most keeps are largely made of stone & brick, the inner chambers often have wooden floors along with any furniture & cabinetry. In addition, during a siege, those working in the woodshop will be making braces to re-inforce weakened walls & spinning out makeshift parts to fix damaged catapults, etc.
The toolshed may also house the tools for stonemasonry such as chisels, hammers and so forth.
Woodshed
The keep will need a large supply of wood, both for construction and fires. To prevent the cut wood from getting wet in the rain, it is likely to be under an overhang at the very least, and possibly even stored in a large "fireproofed" shed. This is very likely to be located in the courtyard in a corner that is far away from any other heat sources to lessen the chances of an accidental fire.
Quarry
In order to build a large stone keep, unless magically created, the stones need to come from somewhere. The most logical place is a nearby quarry. Though not necessarily a part of the castle, it's possible that it is very nearby and actually factors into the keeps defenses. For example, one side of the keep may be adjacent to the quarry and it serves as a large deep pit blocking attack from that side. Once dug out, a quarry is easy to flood. For a more remote location, there may be some outbuildings at the quarry along with some masonry tools, buckets and other ways to assist hauling materials. In that case there's almost certainly a road (or old wagonwheel trails) linking the keep to the quarry as well.
Forest
Lumber and firewood for the keep needs to come from somewhere as well. Though it's slightly easier to haul wood for a larger distance compared to stone due to its lighter weight, it is still very likely that a nearby forest supplies the keep with its wood. Deforestation in the area immediately around the keep is certain to happen during the construction phases, both to supply wood for construction and to make for a more defensible clearing aiding in spotting enemies from a distance away. Once completed, the amount of wood required turns from construction purposes to heat, cooking and fueling the forges. The need for wood will be especially high in the cold winter months. There are likely to be a number of men from the keep that serve as lumberjacks to ensure a healthy supply of wood. Once again, for a more remote woods, there may be shacks for the woodcutters and tools stored there as well.
