GNU Emacs is an extensible, customizable text editor—and more. At its core is an interpreter for Emacs Lisp, a dialect of the Lisp programming language with extensions to support text editing. In addition to a large number of bugfixes, 23.2 includes several new packages, such as the CEDET suite of development tools and a new mode for editing Javascript.

Texmaker is an editor for the document markup language LaTeX. It lets you concentrate on the content of a document, while the underlying LaTeX engine takes care of the layout. Whether you are experienced with LaTeX or just starting out, Texmaker makes LaTeX easier to tame. It is GPL-licensed, cross-platform (running on Linux, Unix, Windows, and Mac OS X), and extremely stable.

"...you can run Elisp (the Lisp interpreter Emacs is built on) programs from outside Emacs [...] This will make Emacs work like Perl or Python or Ruby or Bash—an interpreter that reads the rest of the program and executes the code..." -- nota bene: I love Emacs as a text editor!

"Are you an Emacs user but don't know Lisp?

"EMACS(1) is a real-time display editor which can be extended by the user while it is running. Extensibility means that the user can add new editing commands or change old ones to fit his editing needs, while he is editing. EMACS is written in a modular fashion, composed of many separate and independent functions.

"Many programs have start-up settings, which they read from a configuration file or from some database. Emacs is no exception: when it starts, it reads a file called ".emacs" from your home directory. However, the big difference is that .emacs does not consists of simple "key=value"-pairs. Instead, your .emacs is an Emacs-Lisp (elisp) program itself.

"...Thankfully Emacs has the table mode as part of the standard distribution. Invoke table-mode as M-x table-insert and create the table. Answer the wizard questions and enter the data for the columns. Once you've written the data into the table, generate the LaTeX table by hitting C-^ and choosing the export format as latex..."

"This page shows a example of writing a emacs lisp function that update the page navigation tag of several files. If you don't know elisp, see: Emacs Lisp Basics..."

"This page shows a real-world example using emacs lisp to process HTML files in a directory recursively, searching for a text pattern, and generate a report. If you don't know elisp, first take a gander at Emacs Lisp Basics..."