I actually called my local humane society just a couple of weeks ago to ask them the very same question, OP.
My local HS said that they could not accept anything with elastic on it (like fitted sheets), anything with stuffing or filling (like a comfortor with down or polyester fill), or any pillowcases.
So I cut the elastic off the fitted sheets, and cut the pillowcases at 2 of the seams (one long end, and the short end) so that it would lay out flat like a sheet.
I’m planning on dropping everything off to them today, actually, although I’m not 100% sure what they will/can use. But I figure they can toss what they don’t need/can’t use; or otherwise do what they please with it.
I just hope that at least some of the bedding I’m donating will bring at least a little comfort and warmth to some animals in need. I wish I could take them all home… but since I can’t, I figure that what I can try to do is help where I can.
Although, I my idea of “help” also includes causing physical pain to all of the owners who don’t spay/neuter their pets; and to inflict capital punishment on the assholes who abandon/drop off in the middle of a road or highway (or remote field, barn, wilderness)/neglect/starve/abuse their animals.
But I digress.
I agree with calling them ahead of time to see what they can/can not take; and then donating what they can’t to somewhere like Goodwill or the Salvation Army (if its in “donatable” condition, of course).
Relatedly, I know that one of my family friends who ran a car detailing business was always looking for scraps of material (soft cloth) that he could use to clean and detail the cars he worked on. So there’s another use for scrap material if the HS can’t take it, and it’s not in ‘donatable’ condition.
