Do you hear something going on inside your DVD player when you hit the eject button or not? If you do, try gently sliding another DVD or CD in there at the same time as the stuck one is trying to eject. Sometimes the piggyback effect helps coax the stuck one out.
Preferably use a relatively disposable disc just in case there's a little friction or scratching between the two. A Michael Bolton Greatest Hits CD should fit the bill just fine.