I spent some time today digging into the Persistence and Tracking services available within Windows Workflow.  During my escapades I came across the following set of articles that provided some useful information for building a basic understanding of these two key services within Workflow.  Depending on how some things unfold, we may need to write a tracking and persistence service that works against an Oracle database.  Since we support both SQL Server and Oracle, and since WF doesn't provide base classes and/or interfaces for some key infrastructure classes (SqlTrackingQuery, SqlTrackingQueryOptions, SqlTrackingWorkflowInstance, etc.), we may need to write wrapper classes that allow us to work against a configurable persistence and tracking service. 

Persistence Service

• Windows Workflow Foundation Runtime Services: The Persistence Service
• Workflow Tools
• Oracle Persistence Service
• Performing Transactions in Windows Workflow
• Execute Long Running Workflow Using Persistence

Tracking Service

• Foundations: Tracking Services in Windows Workflow Foundation
• Writing Tracking Services for Windows Workflow Foundation
• Tracking Services Deep Dive