Used stamps to charities

[alriley]

We all save our used postage stamps from time to time to give to charities. But how do charities derive monetary value from these used stamps?

[CiderMonkey]

i asked this as I send our offices used stamps to the British Kidney Association. Apparently, they sell them by the sackfull (they don;t get much for them but it all helps), to the companys that make up those little packs of foreign stamps for stamp collectors.