From New York Times writer Gina Kolata, a discussion of various types of medical studies and how to read them (skeptically). The accompanying graphic is cool too.
From Noël Figart, The Unfit Person’s Guide to Fitness. I found this to be a useful starting place when I began exercising after a few years of not exercising. Lots of fitness resources assume you can already do a pushup or run a few miles. This one doesn’t.