Associations of Writers, Editors and Proofreaders

American Medical Writers Association
Council of Science Editors
Editorial Freelancers Association
European Medical Writers Association
Institute of Scientific and Technical Communicators
International Committee of Medical Journal Editors

Ethics

Annals of Internal Medicine: Ethics Manual
BMJ Collected Resources on Authorship 
National Library of Medicine Ethical Issues in Research Involving Human Participants
Online Ethics Center
Stanford University: Research Policy Handbook On Academic Authorship
Who Should Be The Authors: Guidelines for Authorship of Scientific Papers

General

BMJ Collected Resources on Authorship
BMJ Collected Resources on Journalology
How To Write a Scientific Paper - Susan Cordova
Writing About Research In English: Joan Maclean 
Writing Articles for Medical Journals
Writing Guidelines for Engineering and Science Students Writing in the Sciences

Grammar and Style

American Heritage® Book of English Usage. 1996
Citing Electronic Resources: the Internet Public Library
The King's English: Fowler, H. W.
Guide to Grammar and Writing
Quiller-Couch, Sir Arthur. 1916. On the Art of Writing.
The Columbia Guide to Online Style by Janice R. Walker and Todd Taylor
The Elements of Style: William Strunk, Jr.

Guidelines

ASSERT statement: A Standard for the Scientific and Ethical Review of Trials 
International Conference on Harmonisation: ICH Guideline
The CONSORT statement

Resources

Becoming a (better) medical writer or editor
Books on medical writing
Researchpaper.com
The writing center

Statistics

Bayesian statistics: examples
BMJ Collected Resources on Bayesian statistics: descriptions
BMJ Collected Resources on Other Statistics and Research Methods: descriptions
BMJ Collected Resources on Qualitative Research: descriptions
BMJ Collected Resources on Qualitative Research: examples
BMJ Collected Resources on Randomized Controlled Trials: descriptions
BMJ Collected Resources on Randomized Controlled Trials: examples
BMJ Collected Resources on Systematic reviews (incl meta-analyses): descriptions
BMJ Collected Resources on Systematic reviews (incl meta-analyses): examples
Statistics at Square One