IMO Resolutions

MSC.305(87) - Guidelines on Operational Procedures for the Promulgation of MSI Concerning Acts of Piracy and Piracy Counter-Measure Operations
A.705(17) Amendments - Promulgation of MSI
See Circular MSC.1/Circ.1287/Rev.1 
A.706(17) Amendments - World-Wide Navigational Warning Service
See Circular MSC.1/Circ.1288/Rev.1  
A.1051(27) - IMO/WMO Worldwide Met-Ocean Information and Warning Service – Guidance Document

IMO Circulars

COMSAR/Circ.3 - Relations Between Navarea Co-ordinators and Rescue Co-ordination Centres
COMSAR/Circ.36 - Broadcast of Warnings for Tsunamis and Other Natural Disasters
COMSAR.1/Circ.41 - Analysis of MSI Promulgated Via the EGC SafetyNET System and Recommendations on Improving its Quality
COMSAR.1/Circ.46 - AIS Safety-Related Messaging
COMSAR.1/Circ.58/Rev.1 - Lists of Navarea and Metarea coordinators – 31 Oct 2018
Note that this Circular is updated fairly frequently
MSC.1/Circ.1287/Rev.1 - Promulgation of Maritime Safety Information
MSC.1/Circ.1288/Rev.1 - World-Wide Navigational Warning Service
MSC.1-Circ.1310-Rev.1: Revised Joint IMO IHO WMO Manual on MSI