I agree with many that have already been mentioned - The Wall, London Calling, The White Album, Physical Graffiti, Quadrophenia and The River, certainly. And I’d add Out of the Blue by ELO to the list. One double album that I listened to as much as any of those during my formative years was Jesus Christ Superstar - the original recording with Ian Gillan as Jesus. I really loved that album.

There were some notable double live albums in my collection as well - Fleetwood Mac Live is, in my opinion, much better than any of their studio efforts, and Neil Diamond's Hot August Night is a similarly strong effort (I've taken a lot of flak for liking that album over the years, and I'm not afraid to take more)! Also Queen Live Killers, The Kinks’ One for the Road, Live Rust and The Last Waltz.

If my brother were in on this discussion, he’d definitely include “The Lamb Lies Down on Broadway”, but personally, I never really loved Genesis.

To me, the double album is a distinctly vinyl concept. I don’t think of double CDs in the same way somehow, and now that I’m entirely digital, the whole concept is somewhat meaningless. It’s a shame.