Exploratory testing
From CSTER Wiki
Exploratory Testing Explained, by James Bach. First published as a chapter in The Test Practitioner, 2002 James says "This is an introduction to exploratory testing. It's the latest and greatest I have to say on it, outside of my Rapid Testing Class."
Other articles by James on the subject:
Exploratory Testing and the Planning Myth
Where Does Exploratory Testing Fit?
Session-Based Test Management, which explains how to manage exploratory testing and make it accountable.
