Here's a link that briefly details wood ashes and their uses. I urge you carefully use them in the garden post-collapse. Applying too strong a mix of them, often carelessly dumped in high concentration and not broadcast, will result in soil that is too basic (beyond 7.0 pH). Most plant like that middle zone for growth and producing produce to eat. This means you'll have to fiddle with pine needles (increases acidity) to create more acid soil and it can take awhile to get it back in balance. Be prudent.
[link to oohf.typepad.com
Wood ashes were used to create sterile layers in cheese-making. See:
[link to books.google.com
Black eye shadow was made of soot deliberately made on the back of plates, but also made by wood ash. It may not seem like a survival topic, but honestly a lot of women will be concerned about such things, and this is a coping strategy for feeling some sense of normalcy. The reason women feel insecure about their appearance is because as men we have made them think that to be beautiful they must look perpetually youthful and painted. As men, we should re-evaluate that, and help our women cope better, and raise our daughters better.
Every fire will be put to bed by covering with ashes. These will protect coals so breakfast can be started quickly.
Other than shoveling, those wood ashes will be the primary way of dealing with snow and melting it. This will leach of course into the surrounding as it raises the freezing temperature of the water it blends with and raises the pH. You won't have salt or use salt in this way anymore.