Organizations:
American Medical Writers Association
Drug Information Association
Regulatory Affairs Professionals Society

Regulatory authorities and guidelines:
U.S. Food and Drug Administration
European Medicines Agency
International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use
Consolidated Standards of Reporting Trials

Biomedical journal resources:
International Committee of Medical Journal Editors  
AMA Manual of Style
Strengthening the Reporting of Observational Studies in Epidemiology

Science is fun:
Neuroscience Blog