Microsoft has released on July 13th a revised edition of the Exchange Server 2003 Disaster Recovery Operations Guide.
Some of the things covered in this document are:
What not to backup when doing a full computer backup.
How to backup and restore Databases, SRS, Connectors, and Certificate Authorities.
How to backup and restore Cluster Servers (individually or the entire cluster).
How to restore Windows 2003.
What information about the server you should record before a server fails.