This specification defines the syntax and semantics of XSLT, which is a language for transforming XML documents into other XML documents. (W3C Recommendation 16 November 1999)
XSL is a language for expressing stylesheets. It consists of two parts: a language for transforming XML documents, and an XML vocabulary for specifying formatting semantics. (W3C Recommendation 15 October 2001)
Jeni Tennison is a very active XSLT community member. This page is her homepage for her many XSLT activities. With 25 tutorials/articles and 2 utilities for visitors. Good website.
The successor to Extensible Stylesheet Language (XSL), XSL Transformations (XSLT) is an XML-based language that enables you to transform one class of XML document to another.