Create Smart Playlists for iPods without music in iTunes
You can create smartplaylists in iTunes, which has no matches, but when transfered to your iPod, will match songs from the iPod's library.
This trick is quite handy when using two computers- like a laptop and desktop. If your iPod normally sync's with your desktop at home, but you are on the road with your laptop (and without your master music library), you can connect your iPod to the latptop's iTunes. Just set it to manage your music manually, then create a new smartplaylist containing the criteria you wish to apply to your iPod (but isn't necessarily on your actual laptop).
After disconnecting the iPod, you'll find that the the newly createdsmartplaylist on the iPod is populated on the iPod itself.
Just make sure you don't accidently set your iPod to sync with with your latop- this will wipe out you iPod.