Ah, I've just discovered that some iPods are formatted vfat (as are all Neuroses, iRivers and so on) while others are formatted hfss (wierd harold Mac format). Here for details.

So -- given you have support for the strange Mac filing system -- then

mount -t hfsplus /dev/sda3 /mnt

should do it

if not, try

mount -t hfsplus /dev/sda3 /mnt/

But the url above looks very useful.