This is pretty obvious, but still fun. You can turn your regular hard-drive iPod into an iPod shuffle.
First, make a up a smart playlist called Non-shuffle; you'll need one criterion for each kind of track you don't want to show up on your fake shuffle, such as > Genre > Is > Spoken Word and > Genre > Is > Christmas and such. (This playlist is actually a very handy thing to have for making other playlists out of.)
Then create a new smart playlist called ^ iPod shuffle. (The symbol ^, which is Shift-6, puts the playlist at the very top of the Source window in iTunes and also at the top of your iPod's list.) The criteria will be "> Playlist > Is not > Non-shuffle" and then "Limit to > 1000 > MB selected by > random".
It doesn't really Autofill: once in a while, you'll have to empty out the playlist in iTunes and let it refill. But otherwise it's a pretty good way to mimic the shuffle with a regular iPod. Sticking a post-it note over the screen is optional.