I know: no one buys CDs anymore.
But at $4.99 a pop, Best Buy's collection of budget CDs might be a good way to fill some holes in your library for less than it would cost on iTunes. And remember, you can always upload the tracks to your computer. And let's face it: you need a copy of Abba Live, which would set you back $7.97 on Amazon. This offer is only good online, but my hunch is you wouldn't want to stroll up to the counter and buy an Abba album anyway.
Some other gems include James Brown Live at the Apollo 1962 and a bunch of Rush CDs.
$4.99 CDs at Best Buy with free shipping!