Good no-nonsense advice in the form of questions and answers about BPM. Unlike some overly-technical approaches to BPM, it shows a keen awareness of the importance of business rules and business issues in general.
Be prepared to zoom the text size in your browser.
Another good introduction and overview is Co-ordination Protocol and BPEL, which, despite its title, turns out to be solid business-oriented discussion of BPM issues. Some of the links do not seem to be functioning correctly.
Also see the Weblink for Business Process Execution Language ( BPEL ) on the technical site.