Some songs from iTunes will work. They must be DRM-free. You'll know this because the song will have a plus sign beside it such as this:
. If that logo cannot be seen then you will need to buy the song, burn it to a CD, and re-rip it to get it to play on the Zune. Or, you'll need a software alternative. I can't give you any, though. No video content from the iTunes Music Store will work other than podcasts. The Zune will play .MP4 files, though, which is the format iTunes' videos are in. They are encrypted, which is the only thing stopping you.