Free XSL Tutorials
Another comprehensive tutorial site from w3schools that includes an introduction, overview, tutorial and references.
XSL Transformations (XSLT) Version 1.0
This specification defines the syntax and semantics of XSLT, which is a language for transforming XML documents into other XML documents.
A multi-page xslt tutorial that includes an example page. There is also an xpath tutorials and an xml namespace tutorial.
WSDL processing with XSLT
First steps for Web service description processing.