OpenOffice : OpenOffice comes with Asian language support, you can enable it Tools > Options > Language Settings > Languages > tick the box next to Enabled for Asian languages. Once installed you will also be able to convert text from simplified to tranditional (and the other way around)
Dictionaries
StarDict : this used to be a must have however the project is now discontinued due to copyright infringements (download the gnome 2.2 rpms here locally)
CEDICT : aims to provide a complete Chinese to English dictionary with pronunciation in pinyin for the Chinese characters.
Other software
Chinese Linux Extension (CLE). This extension for RedHat/Fedora gives you a fully functional for linux. [DISCONTINUED]
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. Since 2003 almost all MULE functionalities have been merged into GNU Emacs
hc : This is a program of conversion for BIG5 and GB codes
RedOffice : Was an office suite developed by RedFlag Chinese 2000 software co.ltd (http://www.ch2000.com.cn). [DISCONTINUED]