None of the things I've read have worked.
Sorry...here's what I've tried and what it accomplished: F12 did nothing. The "Eject" button did nothing. Restarting while holding the mouse button did nothing. Restarting while holding down Command-Option-O-F did nothing. Restarting while sliding in a folded piece of thin cardboard did nothing. Going to Disk Utilities and trying to eject from there did nothing.