It used to be the USNWR report for "top medical schools: research" back when it was numerically ranked. But since this was primarily based on research funding and production, some schools rebelled and stopped sending them data. They have since started doing a tiered ranking instead of numerical (tier I schools, tier II schools...). So while this is still somewhat used, it doesn't differentiate between the schools within each tier.
Admit.org created by an SDN user is probably what most applicants use nowadays for numerical ranking. This incorporates a whole bunch of different aspects into the ranking, not just research. I would say it's pretty accurate.
However, unless you are at a very distinct and obvious top 20 (maybe Top 30), or very obviously at the low end of the spectrum (100+), most schools are amongst a group I would call "the average joes". Average Joe schools are solid, reputable institutions with high match rates and produce great doctors. They may not have the big name or the billion dollar endowment, but they make in impact. Anybody at an average joe school will eat what they kill, meaning it's all about what you make of it.
Then there's layman name recognition. For example, Georgetown is a "top 50 ranked school", but telling an average, non-medical person you go to Georgetown will have a similar effect as telling a premed you go to Columbia or Duke.
As always, take any ranking or information about schools with a grain of salt!
