[Fern]

I think FRUGAL acts of kindness refers to acts that actually save someone money.
In the days when i made more $$, i would make donations of $100 or so on a bi-monthlyy basis to my favorite environmental groups like The Nature Conservancy, Audubon, Conservation International or Bat Conservation International.

These days, I can't afford that kind of generosity, but i do still make regular donations to good will and to freecycle.org people. Intentionally dropped pennies might be entertaining for kids to find, but otherwise, you'd need to be dropping a $5 or $10 to make someone's day, i would say.

I also regularly donate books to the 'free' shelf at my local library.