To the many fine albums already mentioned, I’d like to add
Procol Harum: A Salty Dog
Traffic: John Barleycorn Must Die
See, I call that blues-rock. Bands like Wolfmother would fit into that, too, but to me “classic rock” is tied to a time period. Which is excatly why I don’t consider it a genre any more than I consider “Oldies” a genre. Obviously, your mileage varies. For me, Wolfmother and Lenny Kravitz are no more “classic rock” than, say, the Pipettes or Amy Winehouse or another 60s sounding band is “Oldies.”