You know, I was going to vote for BW, but honestly any ranking that does not have Harvard, Stanford & Wharton as the top 3 (in some order) is just kidding themselves; so I went with the US News Rankings. The top 7 in US News jives with Hjort's definition of the ultra-elite cluster and I agree with that. US News also has Berkeley tied at 7, with Dartmouth next after that and I agree that those are the 2 schools most likely to put upward pressure on the ultra-elite schools. I guess I'd put Michigan right there as well.
I just can't agree with BW putting Stanford at 6. Also, I support the idea that Chicago is one of the very best and has been doing a great job improving every aspect of its program. But seriously, it just doesn't pass the smell test to have Chicago (or Northwestern) ranked above Harvard. In terms of selectivity, access to jobs, over reputation, and I'm certain future reputation for the duration of your career, international presence, size and influence of the alumni base, and on, and on, and on, you just cannot go against Harvard. (Note: I'm not saying there's no reason for an individual to select Chicago over Harvard; it just makes no sense to rank them that way).
Hjort's cluster system is probably the best way to consider rankings. If you can get admitted to multiple schools within the same cluster, then just choose the one that you like best and it won't be a mistake. If are admitted to a school in a higher cluster and are leaning towards attending a school from a lower cluster, think seriously about whether that makes sense.
(Just a disclosure, I'm not applying to Harvard.)