XSLT Processors

Oracle XML parser for Java
http://technet.oracle.com/tech/xml/parser_java2/
Saxon
http://users.iclway.co.uk/mhkay/saxon/index.html
XT
http://www.jclark.com/xml/xt.html
Sablotron
http://www.gingerall.com/charlie-bin/get/webGA/act/sablotron.act
Microsoft XML Parser
http://msdn.microsoft.com/downloads/webtechnology/xml/msxml.asp
Xalan Java
http://xml.apache.org/xalan-j/index.html