Not sure if this is new or not but I haven’t notice it before so here goes:
A couple of months ago, Apple added the “Purchased” option to the iTunes store. That option gives you a list of all the apps and books you’ve purchased in the past and gives you an easy way to download those again (for example when you change computers).
Now, Apple has added Music to the Purchased-tab. It show you a list of all the music you’ve purchased through iTunes (either sorted by track or by album) and allows you to download them per track, per album or all music at once.
I seem to remember that getting the music you purchased from iTunes back after a crash used to be a pain in the backside but with this feature that is no longer the case.