FLTK Dock
FLTK Dock is a dockable window framework for Fast Light Tool Kit (FLTK).
http://fltkdock.sourceforge.net/index.html

JX Application Framework
JX -- C++ Application Framework for X
http://www.newplanetsoftware.com/jx/

Haggis
Multi-threaded, concurrent user interface framework for Haskell, X Window.
http://www.dcs.gla.ac.uk/fp/software/haggis/

Window Managers for X: Window Maker
Window Maker page from a guide to window managers and desktops for the X Window System and Linux/UNIX.
http://www.plig.org/xwinman/wmaker.html

DHTML Window
Click here for a window script constructed using pure DHTML
http://www.dynamicdrive.com/dynamicindex8/dhtmlwindow.htm

Ratpoison Window Manager
A simple Window Manager with no fat library dependencies, no fancy graphics, no window decorations.
http://ratpoison.sourceforge.net/

B4Step Window Manager
B4Step is a Window Manager running under X11R6 with a different way to manage window banners. It can use OpenGL routines for animations, is Gnome compliant and has also a sound support.
http://b4step.free.fr/

Akelos Framework
Port of Ruby on Rails development framework and designed to work for PHP4 and PHP5. The purpose of the framework is to support developers in building and managing multilingual database-backed web applications using the Model-View-Control pattern [Open Source, GLPL].
http://www.akelos.org

Zoop Framework
A Object Oriented Framework for PHP, Zoop Framework caters to the programmer and includes ajax and validation. Zoop also features a PHP implementation of .NET controls called GUIControls [Zope Public License, GPL compatible].
http://zoopframework.com

Visual Component Framework
The VCF Website - Online information about the visual component framework, a cross-platform C++ framework.
http://vcf.sourceforge.net