Well, when the "collapse" part of the equation was mentioned, I was considering EMP as a possibility.
One skill (which I keep meaning to get around to) which will survive (or come back) will be amateur radio. If no EMP, then I see a far-flung radio packet/computer network coming about. If EMP, then we'll set up crystal receivers and spark gap transmitters until we scrounge/build enough radio tubes. All that stuff is in books-much faster than having to discover it again.
If collapse, then those with trapping skills will be very much in demand; not so much for meat and skin gathering, but for the millions of suddenly "undomesticated" dogs hunting in packs, and the marauding cats too. There isn't enough ammo to handle our furry former friends.
Anyone who can build and set up a windmill, microhydro, or solar panels will never be hungry ever again; we won't be able to rely on a network of power generation. Even if we could still generate the power, weather and "scavengers" would eliminate most of the lines (easy sources of copper and aluminum, and those tower struts are easily adapted into house frames or whatever).
What else?
-Being able to identify, contain, and clean up hazardous materials.
-Acting, singing, spinning yarns, and other means of entertaining, since Sirius radio and Battle of the Network Stars will be things of the past. Think of Brin's original novel "
Postman.
-Herbalists.
-And I know the general theory of distilling, and how to build a still-purely for fuel purposes, of course.
