Apple's pushed its iTunes Match feature live, with a new version of iTunes (10.5.1) to download that will do the magic. The service, which costs $24.99 a year, gives you iTunes Store-quality and cloud availability of all your music, whether you ripped it from a CD, bought it from another store, or, uh, otherwise acquired it. Apple naturally isn't crowing about that latter possibility, but some see the service as a concession to still-rampant piracy. Unlike some cloud services, Apple uses its own copies of songs that it matches, only relying on your spotty encoding and inconsistent ID3 tags when it comes to songs that aren't in the iTunes Store. That saves Apple on hard drive space, and protects your precious 5GB iCloud storage limit — although Apple allows a maximum of 25,000 songs, and won't let you sign up if you're over the limit. The service is currently beta, and if you sign up now you get an extra three months free, but at the end of the beta you'll have to start over and re-sync everything.
Update: Apple's servers look to be already overloaded, and Apple isn't letting any new iTunes Match subscriptions right now. The remedy? Come back in an hour.