RTAI home page: http://www.rtai.org/index.html
NMT's RTLinux home page: http://www.rtlinux.org/
KURT home page: http://hegel.ittc.ukans.edu/projects/kurt/
Information on all variants of real-time Linux: http://www.realtimelinux.org/
GPL development tools, commercial support and a validated RealTime Linux installation CD: http://www.zentropix.com/