Linux

1. You need to install Chinese fonts (or unicode fonts) and assign them. Install the following packages if you use one of the distributions:
Debian : Arphic TT Chinese fonts, xfonts-intl-chinese, xfonts-cjk and unifont.
RedHat : taipeifonts, ttfonts-zh_CN, ttfonts-zh_TW
Installation guide for X, Mozilla and OpenOffice.org (Chinese)

2. You need an input method editor (perferred is a XIM [X Input Method], specs) like Xcin or Chinput.

3. Set the locale right :
if you don't have the apropiate locales : edit /etc/locale.gen to select the locale(s) you want built, and then run locale-gen.
To enable full support also add following:
$(HOME)/.bashrc
alias ls="ls --show-control-chars"
export LC_ALL=zh_TW.Big5 // To see which locales your system supports : locale -a
export LC_CTYPE=zh_TW.Big5 // LC_CTYPE is an environment variable which indicates how characters should be handled.
export LANG=zh_TW.Big5
export LC_MESSAGES=zh_TW.Big5
export XMODIFIERS="@im=xcin" // XMODIFIERS is an environment variable indicating which XIM server to talk to
stty cs8 -istrip // stty - change and print terminal line settings
stty pass8 // pass8 same as -parenb -istrip cs8

$(HOME)/.inputrc
set meta-flag on
set convert-meta off
set output-meta on

If you are using gnome2 (so also gtk2 en pango 1.2) and xcin, using the following commands to use it in gnome2 programs :
export LANG=zh_TW.Big5
export XMODIFIERS=@im=xcin
xcin& program to run (i.e. xcin& gaim)
(if you add previous lines without the 'program to run' in a .profile -file in the user home directory, xcin will run automatically on login)

• Xcin : xcin is a xim server to perform Chinese input under X.
• XA+CV : Xcin Anywhere, makes that xcin can be used in programs that ar not xim compatible.
• Chinput : Chinput is a Chinese input server on UNIX/Linux
• Minichinput and magicchinput are based on chinput.
• WineInput : an input method that uses microsoft imes through winex.
• UNICON is a Linux kernel enhancement and user-level input software made by TurboLinux.
• Smart Common Input Method platform : is a development platform to make Input Method developers live easier

• the macro's are in a package called cjk-latex for
  debian
  SuSE
• the macro's are in a package called CJK for
  Fedora/redhat (Thanks to Brian Tung for the link)
  RedHat [part of CLE]
  Mandrake, ...
• CTEX (Chinese)
• CJK-Lyx

• StarDict : a must have !!! made for gnome 2.2. (people having problems downloading the rpms can download them here locally)
• CEDICT : aims to provide a complete Chinese to English dictionary with pronunciation in pinyin for the Chinese characters.

• cxterm : cxterm is a Chinese virtual terminal running under X Window System
• cnprint : cnprint is a printing tool for the purpose of changing Chinese text files into PostScript format, of which commands are the same as the standard ones
• cjoe : Joe's Own Chinese Editor
• celvis : Celvis is a vi/ex-like editor on UNIX, which is almost supporting all instructions that vi/ex has.
• Mule : The MULE is an abbreviation of MULtilingual Enhancement to GNU Emacs. In simplicity, it adds some materials to GNU Emacs to make it dealing with multi-languages(encoding systems). It encodes the encoding system of multi bytes again in its inner mechanism; hence, a piece of paper can simultaneously use Chinese(BIG5 and GB), Japanese, Korean, English, Thai, and so on.
• hc : This is a program of conversion for BIG5 and GB codes
• RedOffice : Is an office suite developed by RedFlag Chinese 2000 software co.ltd.

• If you can't view Chinese in Xpdf, you can adjust .xpdfrc (should be in your home dir) and add reference to your Chinese fonts in there.

• Chinese Information Processingi (Chinese, but full with links)
• Gento Chinese Localisation Guide
• Debian Chinese FAQ
• Linux Chinese HOWTO (English version and very old)
• Linux Unicode Programming
• Chinese Unicode fonts for Debian