Everything
You read it right: all the music in one giant, discounted zipfile, available in mp3 or FLAC format (FLAC is a lossless compression that sounds just as good as the versions on the CDs). Please note that you WILL NOT GET CDs if you order this, just an email with a link and some instructions on how to download the files – CDs can be purchased from CDBaby. All the mp3s are totally free of DRM, which means that they will play on any device and in any software that can handle the format. You can burn them to CD, put them on an iPod (or a Zune, god help you), send songs to your friends, etc. And I think there is some kind of cost advantage as opposed to buying them all separately, but honestly I don’t feel like doing the math right now.