The big three are Goucher, Bryn Mawr and Scripps, as you said. They have pretty much a 100% acceptance rate into Medical Schools, and often the most competitive medical schools (Harvard, Hopkins, etc).
Some of the other ones that have more than a 85% placement rate are HES, Columbia, Penn, and really, many others. Its not uncommon for a program to have 80%+ rate into medical school, considering most accept people with a 3.3+, and generally most post-bacs are committed so they do well in the courses.
More than anything, if you're competitive to go to medical school, you can go anywhere. If you aren't competitive, no matter where you go, you won't become competitive. Going to a specific place makes a difference, as graduates from the HES program, Penn program are highly regarded, but a 3.0 from Penn is not going to overcome a 4.0 from Podunk State.
A big reason why the top three programs you mention have 100% placement is because they only accept people who already have the stats and attributes to get into medical school, and I bet those people would have gotten in no matter where they did their post-bac.