I noticed that the April 2006 issue of Microsoft Architect Journal has some interesting articles about workflow - here's an overview:
Building Applications on a Workflow Platform
A workflow is important for resolving business problems. Examine a range of applications that demonstrate the decisions and reasoning architects face when building a workflow platform.
The Amazing Race Metaphor
Today's enterprises realize the potential of automating their business processes. Find out about managing high-level business processes through an analogy to a reality-based television game show.
Exploring Human Workflow Architectures
There are two components of human workflow systems and representative patterns of human-to-business processes interactions. Discover how to apply these components to implement these processes.
Workflow in Application Integration
The integration of applications is one of the greatest challenges architects face today. Take a look at a framework for application integration through the use of tools such as workflow technologies.
Simplifying Design of Complex Workflows
Solid workflow design requires many skills that make workflow a challenge to even experienced architects. Learn an approach for simplifying the design process of complex systems using a new kind of diagram.
Enabling the Service-Oriented Enterprise
Though building lots of Web services can be difficult, managing them can be really difficult. Explore using a model that can assist you with planning capabilities for a service-enabled enterprise.
Service-Oriented Modeling for Connected Systems: Part 1
Architects want to identify artifacts correctly and at the right abstraction level. Check out an approach to model connected, service-oriented systems that promotes close alignment between IT solutions and business needs in Part 1 of a two-part series.
Enabling Aspects to Enhance Service-Oriented Architecture
One of the biggest hurdles to achieving true service orientation is separating the needs of the service from the needs of the application. While services should only be concerned with the business functionality that they are exposing, it is not unusual for application specific features to "leak" into the service layer. We can now overcome the difficulties that have prevented widespread adoption of aspects in practical implementations and enable architects to factor out cross-cutting concerns from the services they are designing.