Every sample mashup in MashZone NextGen contains an <output> declaration and most samples use either <variable> or <input> declarations. Some working samples that may be of particular interest include:
KMLCdataEncoding (cdata.emml) for CDATA encoding variables or output
i4lnFeeds (encoding.emml) for character encoding
VariableScoping (scope.emml) for scoping rules on variable declarations
GoogleWebClipping (webclipping.emml) for handling responses in HTML format
See Mashup Samples for a complete list of sample mashups and where to find them.