Autotoolset is both a colection of small tools (scripts, emacs macros, etc.) to simplify project development with autoconf/automake/libtool/texinfo/emacs and a good documentation on how to get started on these tools and the whole GNU software model.
Cleanux holds different scripts and programs for cleaning up messy code, such as XML and HTML.
EPT (Emacs Package Tool) is full userspace package managing tool for GNU/Emacs.
Integrated development environment implemented with Python and GTK+. Editing components are based on Vim and Emacs.
SrcComDoc allows documentation written in source comment rows to be extracted, formatted and highlighted according to the chosen documentation format. The basic SrcComDoc syntax is source and documentation language independent.
The OO-Browser is an advanced object-oriented class browser with support for browsing C, C++, Common Lisp and its Object System (CLOS), Eiffel, Java, Objective-C, Python and Smalltalk. It runs atop Emacs/XEmacs on Linux, UNIX and Windows.
Lojread is a project designed to aid in the learning of the conlang, lojban. It assists the student in reading the lojban language in such a way that they can build their vocabulary and structural understanding.
Ropeide is an editor for Python source code. Ropeide is written itself in 100% pure Python (Tkinter). Ropeide makes use of the "rope" library (also a sourceforge project).