This is an extremely comprehensive 247 page reference source that explains and gives examples of code, plus the resultant output, for all of the constants, functions, methods, properties, objects, operators, and statements that define this language.
Microsoft's reference site for VBScript covers the basics of VBScript such as data types, variables, constants, operators, conditions, looping, procedures and coding conventions..
This is a mirror of an MS site with reference information for VBScript including keywords, features, functions, methods, objects, constants, operators, properties etc.