Over on Macworld’s forums, member Ice Cold Irony poses a good question:
What fills up the space designated ‘Other’ on your iPod? The size of that section shifts quite a bit and seems to act as a cache while you’re syncing your iPod but otherwise seems kinda weird. Mine is sitting at about 400 megs right now and seeing as I have just over a gig free I’d like to reduce that if possible for the day when I really want the space. So, ya… what takes up the space and how can I reduce it?
The Other entry in iPod Preferences’ Capacity bar generally includes everything that isn’t music, videos, photos, or free space. Specifically its number reflects any iPod games you’ve synced to your iPod, contacts, calendars, and notes; any files and folders you’ve added to an iPod configured for disk use; photos added to the iPod when you’ve enabled the Include Full-Resolution Images option in iPod Preferences’ Photos tab; as well as some files generally hidden from view — database files, for example.
One hidden folder on the iPod contains files that can consume a fair amount of space — the Artwork folder found inside the invisible iPod_Control folder at the root level of the iPod. The contents of this folder — comprised largely of album artwork — can weigh in at hundreds of megabytes.
If you’re concerned about the space consumed by this artwork, you can instruct iTunes to forego it on the iPod. To do so, select the Music tab in iPod Preferences and disable the Display Album Artwork on Your iPod option.