RFC 2646: The Text/Plain Format Parameter - Now-obsolete specification of the "Format=Flowed" solution to reflowing paragraphs in text files. - http://tools.ietf.org/html/rfc2646
RFC 3676: The Text/Plain Format and DelSp Parameters - Current specification for the "Format=Flowed" reflowing paragraphs and avoiding embarrassing line wrap in text files. - http://tools.ietf.org/html/rfc3676
Wikipedia: Plain text - Encyclopedia article about the file format, including applications and encoding details. - http://en.wikipedia.org/wiki/Plain_text
Wikipedia: Newline - Explanation of the representations of new lines used in text files by different computer systems, and how to convert between them. - http://en.wikipedia.org/wiki/Newline
Markdown - Plain text to HTML convertor, relying on standardised but natural formatting syntax in the plain text. - http://daringfireball.net/projects/markdown/