Is there a way to show differences between itunes music library and ipod music library?

I have an ipod touch third generation which hasn't been plugged into itunes for a very long time. It has thousands of songs on it (not purchased from itunes but ripped from CDs)

Over the time I've rated songs. Because it's difficult to remove a song from the ipod directly I have a system whereby I will rate a song one star if I don't like it, and then next time I plug into itunes I remove all one-star songs.

Today I plugged my ipod into itunes. I haven't synced, but I did remove the one star songs.

I would like to also remove those songs from the library in itunes. As there are thousands of songs it will be difficult to do it manually. I guess I could sync, but as I've been burned by sync in the past (all ratings were wiped, and songs I'd deleted were put back) I am scared to sync in order to do this.

So, is there a way to easilly see what songs exist in the library on the computer which are not on the ipod?