Links

http://www.menuetos.org/ - Hail to people who write an entire operating system in x86 assembler! The sources are very well readable, too.
http://www.aros.org/ - Amiga Research OS. A community effort of an API compatible reimplementation of the AmigaOS.
http://www.morphos.org/ - Closed-source, PowerPC-native AmigaOS implementation
http://www.tunes.org/ - Project for a Free Reflective Computing System; an OS without kernel, designed around code that has a knowledge of itself.
http://www.mingw.org/ - A minimal GCC for Windows. An alternative to commercial compilers on this platform, with the well-known compiler core and blessings from Richie.
http://www.lua.org/ - Light-weight embeddable and extensible script language interpreter, developed at the Computer Graphics Technology Group of PUC-Rio, Brazil.
http://www.coplabs.org/ - Frank Pagel's homepage and projects
http://www.oxyron.de/ - Website of the Oxyron group.
http://www.neoscientists.org/ - Server home