GNU Hurd
Bug reports for the GNU Hurd Archives, Debian, Debian GNU Hurd, Edrx's Hurd Page, Free Software Foundation (FSF), GNU Project, GNU Hurd 0.2 Kernel Source Tour, GNU Hurd Hardware Compatibility Guide, GNU Hurd Mailing List, GNU India, Gnu/Hurd
NeXT
Hardware, Software, User Groups, Apple Enterprises FTP site, Intro to NEXTSTEP, Official MiscKit Home Page, Stepwise - OpenStep MiniExamples Library, the Official GNUstep webSite
Flux Research Group: Older Projects and Software
Mach 4 kernel, Lites Unix server, Mach/Lites/4.4-lite, MOSS, Goofie, PA-RISC GNU tools.
Mach
Famous pioneering microkernel research OS, from Carnegie Mellon University: CMU. It lead to many well known OSs: NeXT, Flux (part of the Flux-Fluke-Flask progression, though Fluke is new code, and which is viewed by many as the follow-on to Mach), GNU Hurd.
Maruti
Goal: create an environment for developing and deploying critical applications with hard real-time constraints in a reactive environment. Such applications must be able to execute on a platform of distributed and heterogeneous resources, and operate continuously in the presence of faults.
MK++
Mach compatible microkernel; gives one code base able to support high assurance, scalability, realtime, distribution, SMP, fault handling, performance; all built in an object-oriented B3 evaluable fashion.
MkLinux
An Open Source operating system which consists of an implementation of the Linux operating system hosted on the Mach microkernel.
Real-Time Mach
By Real-Time and Multimedia Laboratory, Department of Computer Science, Carnegie Mellon University. RT-Mach is a resource kernel, a kernel provides resource-centric services, which can then be used to satisfy end-to-end QoS needs.
Real-Time Mach NTT
Another version of Real-Time Mach, by NTT Laboratories. Contains RT-Mach kernel, FreeBSD 2.2.8 server, real-time shell, RT-Java, Hurd loader. Site has fine 'Getting Started' section: readme, release notes, installation, hardware, compatibility, troubles Q&A, contacts.