Here is SecondSpin.com; a place that buys and sells CDs and DVDs. I've never sold them any so I have no idea what they pay, but they have a "Sell to Us" link in the text near the top of the page, that will take you to a page where you can enter an artist, and see what they'll pay for their CDs.

I have purchased from them, and other than relatively slow delivery (I opt for the cheapest method) they have performed flawlessly for me.

Jack

"People generally quarrel because they cannot argue." - G. K. Chesterton