While doing some research on the web I came across a Service Component Architecture Diagram Generator. The script generates diagrams for applications based on the Service Component Architecture (SCA) model. This can be a great aid to understand the relations between components in large BPEL or SOA applications.
Download the tool here. The readme is over here. The script runs on Linux/Unix and has primarily been tested with Oracle Fusion Middleware 11g applications but should work with other BPEL or SOA frameworks.