FBUI is a small, fast in-kernel GUI windowing system for Linux that supports overlapping windows and windows on every virtual console. Its core is currently about 50kB large. See "libfbui" for sample programs and API. This project, while fun and challenging to develop, is now defunct in recognition of the security problems that putting a windowing system inside the kernel gives rise to. The code base remains available, however, in case parts of it may prove useful to the public.
GNUSTEP Live CD contains a lot of software for GNUstep, a free implementation of the OPENSTEP framework (which is also directly used in Mac OS X as Cocoa). It includes excellent applications for RAD (GORM and ProjectCenter). The CD is available for i486, AMD64, Apple Mac PowerPC, and Sun UltraSPARC computers.
libAfterImage is an image import, storage, manipulation, and output library for X. It features support for antialiased, TrueTypei, and X text, a 128-bit internal graphics engine, in-memory RLE image compression, high quality image scaling/flipping/blending, multipoint linear gradients, superior quality image output on X drawables, and much more.
myOS is a minimalistic, OpenGL capable, GNU/Linux-based system without X. It is a bare bones Linux system, stripped of everything but the files necessary to compile and run OpenGL/C code. It has a simplified directory structure and a cleaned-up internal cross referencing. It has two available variants. myOSx-less fits within a 64 MB RAM disk and features a WebKit based on Trolltech's Qtopia demo Web browser. myOSx is oriented for X11, and its development tools are built around Trolltech Qtopia to produce applications based on the WebKit and for the framebuffer of the original myOS system.
The JScrollDesktopPane Swing component for Java provides a virtual desktop replete with dynamic scroll bars, dynamic menus, and dynamic button shortcuts. The JScrollDesktopPane class surmounts the limitations of the original JDesktopPane Swing component, offering a solution to the clipping and overlap problems inherit to said component, and mimics the interface of the original JDesktopPane to provide an easy upgrade path. It provides a scrolling MDI desktop, one of the most requested features to the Java JDK.