Value Stream Mapping (VSM) is a third generation lean process improvement techniques, optimized for an extended organizational transformation effort. It is designed to view the big, macro picture and make strategic decisions with executives. The first generation of this technique comes from Toyota's "information and material flow" (as documented in Lean Thinking and the second generation from Learning to See).
In the context of software delivery, VSM is an excellent tools to holistically analyze and optimize "brownfield" delivery processes, including everything from requirements definition, infrastructure provisioning and application development.
Being derived from Lean Manufacturing, VSM visually represents the way value flows through an organization from the time a customer requests a good/service, until the time a customer receives the good/service. This practice can be particularly effective at:
Some teams prefer whiteboards, but the most common approach uses paper and PostIts
VSM pairs particularly well with Metrics-Based Process Mapping (MBPM) practice. Used together, VSM represents flow of value through a system at a macro level and MBPM represents lower-level implementation steps and processes.
Check out these great links which can help you dive a little deeper into running the Value Stream Mapping practice with your team, customers or stakeholders.