FreeBSD
The freebsd project
http://www.freebsd.org/
Gentoo
Gentoo
http://www.gentoo.org/
Debian GNU/Linux
Debian gnu/linux is a free distribution of the gnu/linux operating system. it is maintained and updated through the work of many users who volunteer their time and effort.
http://www.debian.org/
Cooperative Linux
Cooperative Linux
http://www.colinux.org/
Adamantix
Adamantix
http://www.adamantix.org/
Knoppix
Knoppix
http://www.knopper.net/knoppix/
Libranet
Libranet
http://www.libranet.com/
Suse Linux
Suse Linux
http://www.suse.de/en/
Slackware Linux
Slackware Linux
http://www.slackware.com/
NetBSD
Powerpc, alpha, sparc, mips, sh3, strongarm, hp pa-risc, i386, m68k, vax: of course it runs netbsd.
http://www.netbsd.org/
Linspire
Linspire
http://www.linspire.com/
Xandros
Xandros creates linux operating systems available for home, business and education use. get a live linux os, linux distribution download, or linux desktop from xandros, the easy linux
http://www.xandros.com/