Organizations regarding Susceptibilty testing:

British Society for Antimicrobial Chemotherapy (BSAC) 
Clinical and Laboratory Standards Insitute (CLSI)
The Swedish Reference Group for Antibiotics (RAF)
European Committee on Antimicrobial Susceptibility Testing (EUCAST)

Online Journals:

American Society for Microbiology (ASM)
Journal of Antimicrobial Chemotherapy (JAC)

Other links:

Center for disease control and prevention (CDC)
FDA
World Health Organization (WHO)
NEQAS