I always seem to have about 100-200 megs taken up by "Other", but I'm running out of space for music and now other is at 459.4 MB - valuable space that could be used for Music! What besides the OS is stored here, and how can one clean up?
Sure. So contacts, calendar, mail - that stuff can't possibly take up 100s of megs Unless I have lots of old mail stored here, which I have no problem clearing off the device (though I have no idea how). What else makes up this space?
Are you jailbroken? Sometimes a lot of junk is left behind. Even if u have previously jailbroken. I'm pretty sure you have restore in DFU mode to clear useless files left over in "other".
Album art is also included, IIRC, and iTunes automatically syncs two copies of the artwork for each track to the device - one in the full resolution for when you're on the Now Playing screen, and another as a thumbnail for when you're browsing your music... At least that's what people have posted on here before