Interpreting match lists assumes quite a bit of knowledge, and even as a 3rd year medical student I'm not sure I possess it yet! You need to know which fields are most competitive and also which programs are the top ones in each respective field. For example, if you see a large number of matches in radiology, ophthalmology, dermatology and orthopedic surgery, that's probably an impressive match list. Of course this is a bit oversimplified, but you get the point. It's not too difficult to figure out which are the most competitive specialties...I think I've got that down now...but finding out which programs are the top-tier ones can be quite the arduous task! Perhaps someone else can point you to a good resource, or quickly give you a run down?
I can tell you that Duke has top programs in internal medicine, surgery and ophthalmology, and a not-so-top emergency medicine program since it's only a couple of years old. I'm not sure about our other programs. And I know that Penn has one of the top few pediatrics programs in the country (at CHOP). Maybe we can start a quick little list here for people to add/confirm top programs in particular fields, to help you interpret those match lists.
At the risk of sounding like a broken record though, I'd caution against using match lists to choose a school...in my experience such concerns rightfully weigh in well behind concerns of personal happiness, learning style, location, etc. This doesn't mean you shouldn't choose a top-tier school because you think it would help you match in a competitive field; you just need to make sure you're considering the big picture. In other words, don't choose a school where you might not be happy just because you think it'll help your match chances.