iPods have a very 'user friendly' interface. Usually that's a good thing. However, they are a little close to the ultimate in easy user interfaces which is the single button DWIM. So while I was jogging today, my iPod decided to freeze up on my (I think it was all the jostling, though we'll see as time progresses). And without an off switch, I was at a loss for what to do. There isn't even a recognizeable place to pull out the battery (which is probably good in retrospect).
After some consulting with apples support page I learned the magic keystroke. Hold down Menu and Select (at least on my clickwheel) for a couple of seconds and it will force a reboot (without data loss - whee).