I must confess I'm a big fan of Extreme Project Management, otherwise known as XPM or Agile Project Management, in the right circumstances.
This is not the antithesis to traditional PMI processes; it merely takes a more realistic approach to project situations where there is great uncertainty (like many IT projects) or a severe time constraint (like many IT projects).
The key to making it work is a heavy focus on stakeholders and constant communication. It is anything but a "wing it" approach, as I've written about on PMThink several times. As opposed to "mechanistic" processes, which is the focus of typical Business Process Modeling (BPM), it relies on human interaction management, which addresses "human-driven" processes.
Here's the Wikipedia entry on Extreme Project Management, for more info. Also, be sure to check out the link to Human Interaction Management for examples of human-driven processes.
Extreme project management - Wikipedia, the free encyclopedia