This list is not complete but if someone is willing to add missing bits, feel free.
Maybe it should be on esw.w3.org to make it easier to manage. xhtml 1.0, xhtml 1.1, html 5 http://www.w3.org/1999/xhtml/ xhtml vocabulary http://www.w3.org/1999/xhtml/vocab/ namespace HTML http://www.w3.org/2002/12/namespace xhtml 2.0 http://www.w3.org/2002/06/xhtml2/ svg 1.0, svg 1.1, svg 1.2 http://www.w3.org/2000/svg smil 1.0 http://www.w3.org/TR/REC-smil smil 2.0 http://www.w3.org/2001/SMIL20/ (not clear see [1]) smil 2.1 http://www.w3.org/2005/SMIL21/ (not clear see [2]) smil animation http://www.w3.org/2001/smil-animation xlink http://www.w3.org/1999/xlink/ xpointer http://www.w3.org/2001/05/XPointer CCXML http://www.w3.org/2002/09/ccxml xml: http://www.w3.org/XML/1998/namespace xmlns: http://www.w3.org/2000/xmlns/ Atom http://www.w3.org/2005/Atom Atom Publishing Protocol http://www.w3.org/2007/app MathML 1.0 MathML 1.01 MathML 2.0 http://www.w3.org/1998/Math/MathML/ SOAP 1.2 Envelope http://www.w3.org/2003/05/soap-envelope XML Schema http://www.w3.org/2001/XMLSchema http://www.w3.org/2001/XMLSchema# Web Services Policy 1.5 http://www.w3.org/ns/ws-policy/ WS-Polling http://www.w3.org/2005/08/ws-polling/ WSDL 2.0 http://www.w3.org/ns/wsdl/ http://www.w3.org/2005/08/wsdl WSDL 2.0 CDL http://www.w3.org/2005/10/cdl/ XML Schema instance http://www.w3.org/2001/XMLSchema-instance WSDL 2.0 SOAP Binding http://www.w3.org/ns/wsdl/soap WSDL 2.0 HTTP Binding http://www.w3.org/ns/wsdl/http WSDL 2.0 RPC Style http://www.w3.org/ns/wsdl/rpc WS-Addressing http://www.w3.org/2005/08/addressing/ WSDL Extensions http://www.w3.org/ns/wsdl-extensions/wsdl-extensions.xhtml WSDL Instance http://www.w3.org/ns/wsdl-instance Web Services Policy 1.5 http://www.w3.org/2006/07/ws-policy (deprecated) http://www.w3.org/ns/ws-policy/ RDFS http://www.w3.org/2000/01/rdf-schema# RDF http://www.w3.org/1999/02/22-rdf-syntax-ns# XInclude http://www.w3.org/2001/XInclude XML Fragment http://www.w3.org/2001/02/xml-fragment XML Media Types http://www.w3.org/2004/11/xmlmime XML-binary Optimized Packaging http://www.w3.org/2004/08/xop/include XQuery 1.0 and XPath 2.0 Data Model http://www.w3.org/2005/xpath-datatypes/ XQuery 1.0, XPath 2.0, and XSLT 2.0 Functions and Operators http://www.w3.org/2005/xpath-functions/ XQuery 1.0 http://www.w3.org/2005/XQueryX/ inkML http://www.w3.org/2003/InkML XML Events http://www.w3.org/2001/xml-events Saddle http://www.w3.org/2005/03/saddle/ XKMS 2.0 http://www.w3.org/2002/03/xkms# (a redirection to the spec schema) XML Signature http://www.w3.org/2000/09/xmldsig# (a redirection to the spec schema) XML Encryption Syntax and Processing http://www.w3.org/2001/04/xmlenc# (a redirection to the spec schema) P3P 1.0 http://www.w3.org/2000/P3Pv1 XForms 1.0 WD? http://www.w3.org/2001/08/xforms XForms 1.0 WD? http://www.w3.org/2002/01/xforms XForms 1.0 http://www.w3.org/2002/xforms Attribute Extensions http://www.w3.org/2007/01/attrExt# XProc http://www.w3.org/2007/03/xproc DISelect http://www.w3.org/2005/sel Delivery Context http://www.w3.org/2005/dcn Emma http://www.w3.org/2003/04/emma XSL 1.1 http://www.w3.org/1999/XSL/Format ITS http://www.w3.org/2005/11/its PLS http://www.w3.org/2005/01/pronunciation-lexicon Speech Recognition Grammar http://www.w3.org/2001/06/grammar Timed Text http://www.w3.org/2006/10/ttaf1 (with some sub namespaces) VoiceXML 2.0 http://www.w3.org/2001/vxml [1]: http://www.w3.org/TR/2005/REC-SMIL2-20050107/smil-modules.html#smilModulesNSSMIL20ModuleIdentifiers [2]: http://www.w3.org/TR/2005/REC-SMIL2-20051213/smil-modules.html#smilModulesNSSMIL21ModuleIdentifiers
