JAMA patient page: evidence-based medicine
This week's issue of the Journal of the American Medical Association has a patient page discussing evidence based medicine.
The reading level still seems somewhat high but they do try to explain some of the terms:
"Systematic reviews of the medical literature, large randomized controlled trials (the best way to assess the efficacy of a treatment), and large prospective studies (followed up over time) are types of research published in the medical literature that can be helpful in providing evidence about tests and treatments. Reports of the experiences of individual patients or small groups usually provide less reliable evidence, although they may provide important clues about possible adverse effects of treatments."