TeX-friendly editors and shells

There are good TeX-writing environments and editors for most operating systems; some are described below, but this is only a personal selection:

Unix
Try GNU emacs or xemacs, and the AUCTeX mode (AUCTeX is available from CTAN, but emacs itself isn't). AUCTeX provides menu items and control sequences for common constructs, checks syntax, lays out markup nicely, lets you call TeX and drivers from within the editor, and everything else like this that you can think of. Complex, but very powerful.
MSDOS
There are several choices: You can also use GNU emacs and AUCTeX under MSDOS.
Windows '9x, NT, etc.
Winedt, a shareware package, is highly spoken of. It provides a shell for the use of TeX and related programs, as well as a powerful and well-configured editor.

The 4AllTeX CDROM (see TeX CDROMs) contains another powerful Windows-based shell.

OS/2
Eddi4TeX works under OS/2; an alternative is epmtex, which offers an OS/2-specific shell.
Macintosh
The commercial Textures provides an excellent integrated Macintosh environment with its own editor. More powerful still (as an editor) is the shareware Alpha which is extensible enough to let you perform almost any TeX-related job. It works well with OzTeX.
Atari, Amiga and NeXT users also have nice environments. LaTeX users who like make should try support/latexmk.tar.gz

There is another set of shell programs to help you manipulate BibTeX databases.

alpha
systems/mac/support/alpha.tar.gz
auctex
support/auctex.tar.gz
epmtex
systems/os2/epmtex.tar.gz
TeXshell
systems/msdos/texshell.tar.gz
TeXtelmExtel
systems/msdos/emtex-contrib/TeXtelmExtel.tar.gz
winedt
systems/win32/winedt/winedt32.exe