XML Schema - Info resources

XML Schema Specification - http://www.w3.org/XML/Schema

Using W3C XML Schema Tutorial: http://www.xml.com/pub/a/2000/11/29/schemas/part1.html - brief

XML Schema Tutorial - http://www.w3schools.com/schema/default.asp - more comprehensive

a complete tutorial and other resources available at http://www.xfront.com/files/xml-schema.html