Do you remember the first time you spun Nirvana's Nevermind? I do. I'd pop it in the CD player, and after "Something in the Way", I'd start it again.
At some point I realized there was a whack of time left in the final track, after "Something in the Way" finished. If you let it go, you're rewarded with "Endless, Nameless" after about ten minutes of silence. It's a hidden track.
I always enjoyed discs with a hidden track. One of my favourite tracks on Alanis Morrisette's Jagged Little Pill is the hidden track, "Your House".