Easymacs is an easy-to-learn, one-size-fits-all configuration for new users of GNU Emacs. It sets up key bindings that conform to a common denominator of the Gnome/KDE/OS X/Microsoft Windows human interface guidelines, and provides function-key bindings for other powerful Emacs features. It is fully documented, and the new user can productively edit text right away, without going through the Emacs tutorial. Many commonly-used functions can be accessed without having to learn the "chords" or multiple keystrokes that Emacs uses by default.
Aquamacs is a Mac-like version of the powerful Emacs text editor that runs as a standard OS X application. It features extensive customization that enables it to conform better with Apple's standard Human Interface Guidelines (HIG) than standard versions of the editor do. It provides a more Mac-like user experience than Carbon Emacs.
refdb-mode is a minor mode for Emacs that implements an interface to RefDB, a reference management and bibliography tool for SGML, XML, LaTeX, and Muse documents. It integrates nicely with psgml, nxml-mode, AucTeX, and muse-mode. refdb-mode provides the complete functionality of the RefDB command line clients from a graphical interface. You can add and edit references, notes, and styles, run queries, and insert the results as citations into your DocBook, TEI, LaTeX, or Muse documents. You can also look up cited references in the database right from your document. You can create, transform, and view these documents with a mouse click. This amounts to an integrated authoring environment for markup languages with reference management and bibliography support.
Auto-recompile is a small emacs add-on that allows you to fix compilation errors faster. It does this by continuously compiling the program you are working on while you are fixing problems. It eliminates the need to explicitly start a compilation for every fix you make, and manages your compilations and error lists in the background so that all you have to do is go from error to error and fix them until the program compiles.
cspot is a semantic annotator designed only for the C programming language. It is quite similar to cscope, but some more functionality. It can be used to find the declarations, definitions, and usages of functions, variables, macros, typedefs, and structs. It can also find visible identifiers at some position in the source, functions called by a function, global variables used by a function, usages of local variable declarations, unused global variables, unused function definitions, and more. Because it uses sparse, cspot knows more about semantics than cscope.