LyX is a document processor that encourages an approach to writing based on the structure of your documents, not their appearance. It is intended for people people who write and want their writing to look great without tinkering with formatting details, font attributes, or page boundaries. On screen, it looks like any word processor, but it uses the TeX engine for printed output and producing richly cross-referenced PDFs. It is stable and fully featured.
The ManEdit UNIX Manual Page Editor is an editor specifically tailored for UNIX manual pages. It has a preview viewer, uses the manual page XML format for easy editing, and comes with a tutorial and reference guide. It uses the GTK+ widget set and features syntax highlighting, a complete drag and drop system for easy viewing and editing, a crash recovery system, and sample manual page templates.
METAGRAF is a graphical editor for creating figures in MetaPost. It is currently able to draw any kind of figure in b/w or color. METAGRAF outputs a MetaPost file which can then be run through MetaPost by itself or using TeX. The program is written in Java and is thus platform-independent.
mod_filter allows you to filter output from other modules inside of Apache. This allows you to implement filters (think Swedish Chef, jive, etc.). You can also use it to retailer output for your locale. This works with HTML documents, mod_perl, PHP, JServ, CGIs, and for that matter just about any sort of custom handler you might have.
The SeaMonkey project is a community effort to develop an all-in-one Internet application suite. It contains an Internet browser, email and newsgroup client with an included Web feed reader, HTML editor, IRC chat, and Web development tools, and is sure to appeal to advanced users, Web developers, and corporate users. It uses much of the Mozilla source code powering such successful siblings as Firefox, Thunderbird, Camino, Sunbird, and Miro.