This should work on just about any Ipod (except the shuffle.... Duh!)
Step 1: ReBoot It
same time for about 6 seconds.
The Ipod should reboot.
Step 2: Bring It Into Diagnostics Mode
It may take a while to load into diagnostics so don't take you fingers off of the buttons for about ten seconds, If it brings up the main menu before then you can stop (it didn't work).
You'll know that it worked if you see something akin to the picture below.
It took me about 6 times to get it right so don't feel frustrated, the touch wheel buttons are really sensitive and the commands don't always work...
Step 3: Have Fun!
has an option to put the iPod into hibernation, the closest thing I can find to turning it off if I need to
store the batteries.