MSXML XSLT FAQ - Unofficial FAQ with answers to questions about XSL/XSLT on the Microsoft platform.

XSLT Test Tool - Tool that allows you to edit XSLT and compare the major XSLT processors side-by-side (windows only).  The tool and installer currently support the following XSLT engines: Microsoft MSXML3, Saxon, Xalan, Oracle XSL, Sablotron, Xt, Unicorn, Napa, 4XSLT, and Instant Saxon.

XSLT Processor installer - Downloads and installs all of the major XSLT processors available and lets you get started using right away.  Crude and simple, but usually works (windows only).

XSLT for OPML - Using XSLT with OPML (all platforms).

Weblog - "Better Living Through Software"

Whitepaper - "Making the Web Semantic"