As far as I know, there is no way to transfer songs from ipod to itunes library directly using itunes alone. So, there are tones of different softwares out there doing this transfer. You can simply google Ipod to itunes.
i did this once without any help with any software, just because i did this massively.
my computer > ipod drive(right click) 可攜式裝置something like that > IPod Control > music
there are all your songs and videos, so copy them and put them in itunes library.
itunes library: my documents > my music > itunes > itunes music
and set your itunes perference to 'keep itunes library organized'
then go to itunes Files > add folder to library > then select the itunes music folder
DONE
thats what i did
hope it helps
