Arora is a simple cross-platform Web browser whose feature list includes things like "History" and "Bookmarks". It has a small code base. It was originally created as a demo for Qt to help test the QtWebKit component and find API issues and bugs before the release. A very old version can still be found in Qt's source code in the demo/browser directory. Arora works on Linux, OS X, Windows, FreeBSD, and embedded Linux using Qt Embedded, and works anywhere else Qt does.
CHM Reader is an extension to allow Firefox to read Compiled HTML (.chm) files. After installation, with "File | Open CHM File", you can open a CHM file in Firefox. With "View | Sidebar | CHM Reader" or "Ctrl-E", a sidebar that contains topics and an index of the CHM files will be shown.
Firekeeper is an intrusion detection and prevention system for Firefox. It is able to detect, block and warn the user about malicious sites. Firekeeper uses flexible rules similar to Snort ones to describe browser-based attack attempts. Rules can also be used to effectively filter different kinds of unwanted content.