YAML - YAML 1.2 --- YAML: YAML Ain't Markup Language
Markdown by DaringFireball - Text-to-HTML conversion tool/syntax for web writers, by John Gruber
TOML - TOML - Tom's Obvious, Minimal Language
GitHub Flavored Markdown - GitHub uses "GitHub Flavored Markdown," or GFM, across the site--in issues, comments, and...
JSON - (JavaScript Object Notation) is a lightweight data-interchange format
Texy! - Texy! is a lightweight markup language as well as converter of this format to XHTML, in a form of a...