Check out Zamzar.com, a free online file converter website where you can download songs from Youtube right to iTunes!
At first I thought it was too good to be true, but then I tried it when I had to download some music for a PowerPoint for my internship and I didn't want to purchase the songs. All you have to do is find the song on Youtube and copy the URL, tell Zamzar what file you want it in, put in your email address and convert. You'll get a link to download in your inbox and it can go right to iTunes, ready to listen.
Tell me, have you ever used this? What is your favorite way to get new music when you're broke?