iTunes sells and rents copyright protected content. iTunes content (with few exceptions) is not free or in the public domain.
Nonetheless, iTunes can be an excellent tool for making audio and audio-video materials available to your students at a very low cost. You cannot embed these materials in your courses, but you can link to a playlist called an "iMix" in your course. When your students click on the iMix, they can preview the contents and then buy them (in the case of music) or rent them (in the case of most videos.)
Audio files are 99 cents, and audio-video rentals are $1.99 to $3.99. You should approach your Center administrators about funds to explore content that you would use in your courses, and costs to the students should be taken into account the same as costs of purchasing textbooks and course packs.
You and your students will need to have the iTunes music player (version 4.2 or higher) installed. It is available here.
Instructions on how to create an iMix are here.