User-friendly introductory material can be found at the main R website on the Contributed Documentation Page.
The Consort Group is a collective of clinicians, epidemiologists and statisticians whose aim is to improve the conduct and reporting of randomized clinical trials. They have developed a set of suggested guidelines known as the Consort Statement. A subsequent document provides more detail, especially with regard to the statistical analysis of clinical trials.
Epidemiology is a key ingredient in the background of any biostatistician. There is a wealth of educational material on the WWW. Epidemiology for the Uninitiated provides a concise introduction. The Epidemiology - Internet - Global Health site contains a host of more extensive and specialized material.
CAUSEweb.org is a great resource for teaching resources in general, including this collection of links compiled by Juha Puranen of the Department of Mathematics and Statistics at the University of Helsinki which points to a number of sources of data.