Emacs isn't just a text editor; it's a complete user environment supporting multiple windows, language-specific editing, and an extension language. It is also well on its way to becoming a major religion among UNIX users.
Emacs is powerful and flexible. It supports arbitrary line lengths, an unlimited number of edit buffers, and it handles both ASCII and binary files. It has mode-specific and buffer-specific key bindings that give the user full control over nearly every key. Emacs also works well as a programming environment, providing syntax-specific support for more than a dozen languages.
The definitive freeware Emacs, GNU Emacs is available by FTP from GNU archives at MIT (ftp://prep.ai.mit.edu/pub/gnu/) and other sites. The basic Emacs distribution is emacs-*.*.tar.Z. The Emacs Lisp and Emacs manuals are also available (elisp-manual-*.tar.Z and emacs-manual-*.dvi.Z), but you are better off ordering printed copies from the Free Software Foundation (FSF) in Cambridge, MA.
The FSF supports the GNU Emacs development effort by distributing GNU software on tape and selling printed manuals for many GNU packages. No matter how you get GNU software, please send some money to the FSF, so they can continue their fine development and support efforts.
If you like X, you may be disappointed by the level of mouse support in Version 18 of GNU Emacs. Version 19 promises to resolve this, but if you are in a hurry, consider picking up Epoch (University of Illinois; ftp://cs.uiuc.edu/pub/epoch-files/epoch/) or XEmacs (formerly known as Lucid Emacs): ftp://cs.uiuc.edu/pub/xemacs/) or http://xemacs.cs.uiuc.edu/).
Like UNIX, Emacs has spread worldwide. The MULtilingual Enhancement to GNU Emacs (Mule) supports editing in languages other than English. You might guess from its archive location (ftp://etlport.etl.go.jp/pub/mule/) that Mule is well suited to Japanese. It supports ASCII characters (7 bits) and ISO Latin-1 (8 bits), as well as Japanese, Chinese (GB and Big5), and Korean (16 bits) characters coded in the ISO2022 standard and its variants (e.g. EUC, Compound Text).
Emacs Lisp (commonly, though incorrectly, called Elisp) is GNU Emacs' powerful extension language. Ohio State University has the largest archive of Emacs Lisp code (ftp://archive.cis.ohio-state.edu/pub/gnu/emacs/elisp-archive/). The summary file, LCD-datafile.Z, contains over 800 entries. These include games, specialized editing modes, mail and netnews readers, a desk calculator, and assorted text filters.
Because volunteers maintain the archive, the versions at OSU may not be the most current. Use OSU's version as a starting point, then check around, if desired, for a more current copy.
Hyperbole is one of the more adventurous E-hax I've seen It is a prototype hypertext system developed by Bob Weiner of Brown University. As Bob describes it: "Hyperbole is an open, efficient, programmable prototype information management system with a hypertextual flavor." Hyperbole can be found on ftp://ftp.cs.brown.edu/pub/hyperbole/.
The GNU Emacs distribution contains a substantial list (.../emacs/etc/SERVICE) of commercial support providers. Cygnus Support (Mountain View, CA), the largest of these, provides commercial support for a range of GNU software, including GNU Emacs.
UniPress Software (Edison, NJ) has written a commercial Emacs, based upon the original C language Emacs created by James Gosling. It has X windows support with multiples frames, scroll bars, etc. The extension lanaguge is Mlisp, another dialect of Lisp. UniPress has binary versions for many system types, and also has European (8-bit) and Kanji (16-bit) versions.