Spotify would work, but I know that Led Zeppelin's catalog is not on there, so right out of the gate you can't claim to represent the history of rock in riffage without them :/
http://html5.grooveshark.com/ Search up a song, click on 'play next' and it gets added to a que. I haven't played around with it that much, so I'm not sure if you can save playlists or not. But it's a good way to find free songs without adds and commercials.
I <3 Spotify. I pay for a subscription, and it's totally worth it. Also, the paid version transforms the service. Amazingly better without adds, nice paid feature set, plus their catalog is probably the best of any online streaming service out there.
- It's the first thing I've actually paid for like this. I don't find things like Hulu Plus and other monthly payments for online services worth the money.
Me too. In fact, I would consider myself vehemently opposed to paying for subscription services. Yet Spotify I find completely worth it, -more than Netflix even, which is the only other service I pay for.