Moving music from a 3rd Generation Ipod to Itunes

All,

In the process of clearing out some stuff in my house, I ran into an old ipod classic (80GB) that I had misplaced. I have some music on it that for some reason is not in my current iTunes collection. My question is on the best way to move them into iTunes, without synchronising the iPod and losing the music that I currently have on it. Any and all pointers would be greatly appreciated.

Thanks,

Nedu