For what it's worth, I've had this exact same problem, but I didn't wait it out. What I did was stick a credit card into the CD slot, very very slowly, until I could just barely feel the edge of the disc spinning. I pressed the card against the disc ever so slightly and the disc stopped spinning. The drive made the normal eject noises and presto! They disc ejected and the computer booted normally.
Obviously it's a risky method, but it has worked for me. Just make sure you are pressing the card against the front of the disc and not the data side.
I've also had luck ejecting a disc that wouldn't mount on the Desktop by putting the computer to sleep and holding the Eject key to wake it. This doesn't always work, though.