When I still used CDs (god, I hate the freaking things) they were sorted as such, on a 6-tier entertainment unit:
1 - Mix CD's, pirated / discs I made using more than one artist.
2 - Studio albums, legitimate, 1-2 stacks/studio albums, pirated, 1-2 stacks
3 - Box sets of things/anthologies or anything coming in a large package
4 - Greatest hits compilations, legitimate, 1-2 stacks/pirated compilation packages
5 - Legitimate various artists types of CDs
6 - Cassettes (which don't count, but I have a shit load of them)