Hopefully, all you iPodders (please don't sue me Apple) know that they give away a free song every week on iTunes. You can always delete the song if you don't like it. Why pass up on 52 free songs every year? And every once in a while you can find a Discovery Download - an artist that has been deemed buzzworthy.
Also, now that they're adding more video content, there's even free tv shows and short movies. This site has compiled a list of the current offerings: