Seem to have forgot to blog these and considering many people are searching for them, here is a link to the Exchange 2010 architecture diagrams:

• Microsoft Exchange Server 2010 Transport Server Role Architecture Diagrams
  (on the Hub Transport Server and Hub Transport extensibility)

Unfortunately, the Exchange 2007 Component Architecture and Edge Transport diagrams haven’t been updated for Exchange 2010. For archival purposes, here are the links to the Exchange 2007 diagrams:

• Exchange Server 2007 Component Architecture
• Microsoft Exchange Server 2007 Transport Server Role Architecture Diagrams
  (on Hub Transport, both RTM and SP1, and Edge Transport)