aee is a text editor that is intended to be usable with little or no instruction. It provides both a terminal (curses based) interface and native X-Windows interface (in which case the executable is called xae). Features include pop-up menus, journalling (to recover from system crash or loss of connection), cut-and-paste, multiple buffers (associated with files or not), and much more.
Anjuta is a versatile Integrated Development Environment (IDE) for the GNOME desktop. It features a number of advanced programming facilities that include project management, application wizards, an on-board interactive debugger, an integrated glade UI designer, integrated devhelp API help, an integrated valgrind memory profiler, an integrated gprof performance profiler, a class generator, a powerful source editor, source browsing, and more.
ArgoUML is a pure Java open source UML CASE tool that provides cognitive support for object-oriented design. ArgoUML provides some of the same editing and code generation features of a commercial CASE tool, but it focuses on features that enhance usability and support the cognitive needs of designers. Uses XML file formats: XMI and PGML.
Beaver is an Early AdVanced EditoR, for Linux and other Unices (and even Windows); in other words, it's a text editor that is intended to be light-weight, but full of useful features for programming, from editing of web sites to C coding. It is based upon the GTK+ toolkit, supports many languages, and offers functions such as automatic indentation and syntax highlighting.
Bibcursed is a simple curses-based editor for BibTeX bibliography files, especially useful for those who have to maintain a large number of references for a major piece of documentation, like a PhD thesis. It performs everyday functions such as adding, removing and viewing reference entries. Intelligent prompting for fields is used when adding entries so that authors do not have to rely on memory for knowing which fields can and cannot be used for different entry types.
BlueJ is an interactive Java development environment. It provides a unique user interface that presents a graphical display of the application classes and their relationships, and it lets users interactively create objects of any class. Once objects have been created, users can interact with them directly. This interaction mechanism allows for much greater testing and experimentation than in conventional environments. BlueJ is suited for teaching and learning OO and Java.
CMUCL is a free, high performance implementation of the Common Lisp programming language which runs on most major Unix platforms. It mainly conforms to the ANSI Common Lisp standard. CMUCL provides a sophisticated native code compiler; a powerful foreign function interface; an implementation of CLOS; the Common Lisp Object System; which includes multimethods and a metaobject protocol; a source-level debugger and code profiler; and an Emacs-like editor implemented in Common Lisp. CMUCL is maintained by a team of volunteers collaborating over the Internet, and is mostly in the public domain.