Comments on 10111 | Ask MetaFilter: "Here's what I did: after I had checked/unchecked all the songs I wanted on my iPod, and found out that also means those songs are skipped in playback, I was in the exact same situation. So I create a smart playlist included only checked songs with bitrate > 0kbps. Then, I copied that playlist to a new (dumb) playlist called 'iPod Songs'. Et voila, you can now check all the songs in your library again so they'll play normally.
Also, if you create a smart playlist 'iPod Rejects' that just contains songs not in the 'iPod Songs' playlist, you'll now have an easy way to add and remove songs from the iPod. Plus, with all the iPod songs in their own playlist, you can see the exact size of that collection so you don't have to guess any more about whether or not they'll fit on the iPod."