Funny you should ask...
First, I'm keeping all originals, but tossed the jewelcases. That freed up 10x the amount of space previously taken up, then I placed them on a spindle.
just this morning I "donated' nearly 1000 burned discs (audio and data) to a friend at work.
Last night, what few cassettes I had left were also donated to someone (who is overjoyed at now owning Kate Bush on tape).
Ebay is a horrorshow and used cd stores won't give you shit. I've been paid in happiness.
The vinyl....ask me in a few months...