Deep Dive into the SharePoint Content Deployment and Migration API

http://blogs.technet.com/stefan_gossner/archive/2007/08/30/deep-dive-into-the-sharepoint-content-deployment-and-migration-api-part-1.aspx

SharePoint Planning Visio Diagrams

TECHNET - Technical diagrams and other supplemental documentation

http://technet.microsoft.com/en-us/library/cc263199.aspx

Models
Model: Business Intelligence
Model: Office SharePoint Server Application Security
Model: Office SharePoint Server Backup and Restore
Model: Office SharePoint Server Topologies
Model: Office SharePoint Server Baseline Site Hierarchies
Model: Office SharePoint Server Customization
Model: Office SharePoint Server Database Administration
Model: Office SharePoint Server Enterprise Content Management
Model: Office SharePoint Server Extranet Topologies
Model: Office SharePoint Server Inter-Farm Shared Services
Model: Office SharePoint Server Products Migration
Model: Office SharePoint Server Search Administration
Model: Office SharePoint Server Shared Services
Model: Upgrading Office SharePoint Server Products
Model: Upgrading SharePoint Portal Server 2003 to Office SharePoint Server (1 of 2)
Model: Upgrading SharePoint Portal Server Version 2 to Office SharePoint Server (2 of 2)

Scenarios
Scenario: Enterprise Content Management
Scenario: InfoPath Forms Services Customer Interaction Form
Scenario: InfoPath Forms Services Expense Reporting
Scenario: InfoPath Forms Services Insurance Claims
Scenario: InfoPath Forms Services Permits
Scenario: InfoPath Forms Services Supplier Survey
Scenario: Keeping Connections to Data Sources Current
Scenario: Large Corporate Internet Site (Infrequent Changes to Web Content)
Scenario: Office SharePoint Server Call Center
Scenario: Office SharePoint Server Corporate Intranet Portal Site
Scenario: Office SharePoint Server Departmental Portal Site
Scenario: Office SharePoint Server Equities Research
Scenario: Office SharePoint Server Informational Portal Site
Scenario: Office SharePoint Server Out-Hosted Portal Sites (ASPs)
Scenario: Online News Internet Site (Frequent Web Content Updates and Searching)
Scenario: Preserving “One Version of the Truth” for Distributed Workbooks
Scenario: Records Management in Office SharePoint Server
Scenario: Rendering Data from Spreadsheets to Web Parts

Flowcharts
Office SharePoint Server Planning Flowchart, Part I (application administrators)
Office SharePoint Server Planning Flowchart, Part II (IT pros)
Office SharePoint Server Deployment Flowchart

For more on Visio and SharePoint, see:
Integrating Visio 2007 with Microsoft Technologies
Visio Services and SharePoint 2010