Some of us don't need a reason to buy more music. But after perusing some of the albums over at iTunes Greatest Albums Sale we got the same feeling we used to get searching the "Used CDs" bins back in college. Why don't I own this? With music ranging from Johnny Cash to Jeff Buckley, they've covered a lot of the classics. We began to wonder what we had forgotten to include in our digital music collection. And even if you procur your music in another form, it's fun to look to see what they've classified as a "Great Album."