Handy XSLT Reference Site focused on specific tasks
I've used the information on this site for years now (in addition to Michael Kay's XSLT books). The site has gathered responses by some of the best XSLT professionals, to common XSLT-related questions / tasks .
Dave Pawson's XSLT Questions and Answers: http://www.dpawson.co.uk/xsl/sect2/sect21.html