We donated my old car here:
http://carshelpingveterans.org/veteran-car-donation-faq.php
It was super easy. I just called and set up a time for them to come out. I didn't even have to be there. Left the title and the key in the glove compartment. They towed the car and mailed the license plates back to me. A couple of months later I got the tax form I needed showing they sold it for $900 so I was able to claim that on my taxes. It was a '99 Mazda Protege that had a spare tire on it (some asshole STOLE MY FUCKING TIRE FROM MY CAR) and wasn't even running (battery dead). It had 150k miles and needed a new coat of paint (no rust...but the clear topcoat was peeling). To be honest, I was shocked they even got $900 for it. Ha ha ha!
Honestly, though, I was so happy to just get it off my hands and off my insurance. It wasn't worth the hassle of trying to sell.