Recovery boxes.

[Matt W]

Small cache: several water-quality test kits, several books on useful topics (mostly health guides like "When there is no Doctor"). At least one windup radio


These caches should be plentiful. They would be enclosed in a PVC cylinder. about 1metre long 20 cm wide and in an easily accessible and standard location - for example - "in the parking lot of XYZ grocery, under the concrete trash bins" . This location should be freely given to survivors. No need to keep them secret.
:
Medium caches: Tools for clearing roads and a "radio station in a suitcase" . Also some more advanced books on health and engineering.
This would be a 1 metre cube. buried beneath a billboard

Large cache: Now this will need thought and perhaps a list :-)