Does anyone know if there's anything in place here for donating used stamps?

In UK they can be handed in to various charities and the money raised by selling them on is used by said charity, for example going towards buying guide dogs for the blind.

We get a lot of stamps at this time of the year on our Christmas cards and it seems such a shame to just throw them out.

I don't think there is - I collect all our stamps and take them back to the UK to be given to Charidy.....perhaps you could mail them over to someone and they could forward them on to the correct people?