Are there any articles explaining Cocoon technologies, apart from the Cocoon documentation itself?
Yes. In XML Magazine, Fall 2000, there is an article entitled “A Better Way for Web Development” by Kevin Jones, from page 72. This article discusses XML, XSLT, Using XPath in XSLT, processing XML/XSLT, using Cocoon, how to write a Producer and other helpful hints. Although incomplete in one important respect (lacking a mention of XSP!), it’s a good introductory read.