Applications

ActiveState Komodo
Professional IDE for open source languages, offering support for Perl, PHP, Python, Tcl, and XSLT.
http://www.activestate.com/products/komodo_ide/

Link Toolbar
An add-on toolbar for mozilla that implements parsing of the <link> element for HTML
http://segment7.net/projects/mozilla/linktoolbar/

Mozilla Amazon Browser (MAB)
A tool for searching and browsing the Amazon database.
http://mab.mozdev.org

Mozilla XUL Runtime Project
Project aiming to create a XUL runtime that requires no browser.
http://developer.mozilla.org/en/docs/XULRunner

PrefBar
The Preferences Toolbar for SeaMonkey, Mozilla, and Firefox allows for quick changes of frequently accessed preferences.
http://prefbar.mozdev.org/

Venkman Project Page
JavaScript debugger extension for Mozilla and Netscape browsers.
http://www.mozilla.org/projects/venkman/

XUL Applications
XUL applications/utilities for Mozilla (and Netscape 7). They are based on the specification of Mozilla Nightly Trunk. Works on Netscape 7.0, Mozilla 1.0, Phoenix 0.5, or later.
http://piro.sakura.ne.jp/xul/xul.html.en

ZopeStudio
A management and development environment for the Zope application server.
http://www.zope.org/Products/ZopeStudio/

ZULU
A layout engine for producing rich cross-platform user interfaces, using XUL standard and Flash MX technology.
http://zulu.netspedition.com/zulu/main/overview.shtml