Puniz indexes music, download the video and add to iTunes = Free Music
I wrote a post about how to record your system audio to get music for free and this is along the same lines. Puniz indexes music from all over the web. Most of the music is attached a video and all you have to do to add it to itunes is save the video as an MP3 and then add it to itunes. It's free music perfect for getting those popular singles and pop songs that you don't want to purchase the whole album for.
Puniz allows you to search by song, artist, or keyword to find the song you want. When you click on a song you are sent to a page where you can listen to the song and download the video. I downloaded some songs opened the video in quicktime and exported it as a AiFF file added it to itunes and then converted the song to an MP3. It's a quick and easy way of finding songs and with a little bit of work can get into a format that iTunes will be happy with.