Roger L. Costello a brilliant thinker, about XML and related technologies, has recently posted extensive study materials related to XML Schema 1.1, on his web site (ref, http://www.xfront.com/xml-schema-1-1/).
Roger mentions, Saxon 9.2 as one of the products that implements XML Schema 1.1 features.
From the information I have from Apache Xerces-J developer's forum, I am happy to share with the community, that Apache Xerces-J is planning to release, a preview of XML Schema 1.1 implementation, by around the end of this year (i.e, Dec, 2009). A latest snapshot of Xerces-J XML Schema 1.1 source code repository and related dependencies, is located at, https://svn.apache.org/repos/asf/xerces/java/branches/xml-schema-1.1-dev/. User's are welcome to build binaries from the sources, available here and try XML Schema 1.1 features, currently implemented in Apache Xerces-J. Much of the XML Schema 1.1 features, are implemented at this Xerces-J snapshot URL.
1) XML Schema Definition Language (XSD) 1.1 Part 1: Structures
2) XML Schema Definition Language (XSD) 1.1 Part 2: Datatypes