ZIP

RFC 1951: DEFLATE Compressed Data Format Specification version 1.3
Specification for the most common compression algorithm used in zip files.
http://tools.ietf.org/html/rfc1951

ZIP File Format Specification
Application notes describing the zip file format, its methods, layout, and data.
http://www.pkware.com/index.php?option=com_content&task=view&id=64&Itemid=107