I have already spoken to my local branch of Oxfam, which specialises in books, vinyl, CDs and DVDs.
I told them I could have at least 500 CDs to donate, and probably about a couple of hundred DVDs. In the words of the assistant there: "We'll take everything you've got. Just don't bring it all in one go." So I'm drip-feeding them, as I work my way through the alphabet.