Free Alternatives
Amiga Research OS
Arch Linux
Ares Desktop
BeOS Max
BeOS Personal
BlueCat Linux
Brix
Calyptos
Cefarix
Clicker32
ClosedBSD
Conectiva
Coyote Linux
CP/M
Darwin
Debian GNU/HURD
Debian GNU/Linux
Debian GNU/NetBSD
DragonLinux
eCos
EnGarde Linux
ERIKA
EROS
Fedora Core
Fiasco
FIRE
FlightLinux
FreeBSD
FreeDOS
GazOS
GeekOS
GEM
Gemini Nucleus
GenSTEP
Gentoo Linux
GNU/Lesbian Linux
Immunix
IPCop
JBLinux
KNOPPIX Linux Live
Komodo
KRUD
Kurumin Linux
LainOS
LibraNet Linux
Linux Antarctica
Linux From Scratch
Linux Router Project
Lycoris Desktop/LX
Mandrakelinux
Mandrakesoft Business
Menuet
Minix
MkLinux
Mobius
ModulOS
Momonga Linuxd
NetBSD
NewOS
Oberon
Odin
OpenBeOS
OpenBSD
OppcOS
Peanut Linux
PicoBSD
Plan 9
PM_SZ_OS
PowerOS
ReactOS
RDOS
Red Flag Linux
ROCK Linux
Rome
RTEMS
S.Ha.R.K
SkyOS
Slackware Linux
SmoothWall Express
SOT Linux
Spinix
Stampede Linux
Syllable
Tinfoil Hat Linux
TurboLinux
Unununium
Vector Linux
Visual Network OS
VSTa
WINE
WinLinux
Wolverine
Xandros
XTeam Linux
Yellow Dog Linux
yellowTAB Zeta
Yoper

Commercial Alternatives
AIX
AmigaOS
eComStation
Hancom Linux
HP-UX
IBM PC-DOS
IRIX
Linspire
LynxOS
Mac OS X
Mac OS X Server
MontaVista Linux
MorphOS
Novell NetWare
OpenVMS
OS/2 Warp
PhatLinux
QNX
Red Hat Desktop
Red Hat Enterprise Linux
RISC-OS
SmoothWall Ltd.
Sun Java Desktop System
Sun Solaris OS
SuSE Home Users
SuSE LINUX Server
Tru64 UNIX

MS Office Alternatives
602 Pro PC Suite
AbiWord
Ability Office
AppleWorks
EasyOffice 2001
GoBe Productive
Hancom Office
KOffice
Lotus SmartSuite
OpenOffice.org
Ragtime
Softmaker Office
StarOffice
SOT Office
ThinkFree Office
WordPerfect Office
WorkDesk Office

Browser Alternatives
Arachne
Beonex
BrowseX
Camino
CrazyBrowser
Dillo
Firefox
Galeon
iCab
K-Meleon
Konqueror
Mozilla
Netscape
Off By One
OmniWeb
Opera
Safari
Skipstone