If you use Linux and want to bust out your old iPod (or even go and pick up your first one), until now your options have been to run iTunes in a VM, or flash it with RockBox, which is a whole thing in itself.
But now http://tunesreloaded.com/ exists, and it's a wondrous thing! Just hook up your iPod, drag some tunes over, hit sync, and there they are, ready to play.
There are two caveats: Firstly, it's currently Chrome/ium only, secondly, the iPod has to have been synced with iTunes at least once. But assuming you're able to satisfy those two requirements, we now have an easy way to sync music to our iPods!