Gul is a Xul-like / easy glade-like XML markup language for describing user interfaces with PHP-GTK extension. Gul simplifies writing client-side GUI applications. CSS is partially supported.
The DUML project is 3 sub-projects: 1) Document Update Markup Language (DUML) which allows for updates of the DOM via server markup 2) Interpreted Application Markup Language (IAML) which provides markup based widgets. 3) A set of common libraries (JAS).
Scratch is a simple markup language for use in applications such as weblogs and content management systems. Scratch provides simple inline and block tags for formatting and semantic markup.