Emacs, the infinitely extensible text editor
Emacs has a mode for TeX and LaTeX, in which it will automatically produce smart quotes, match parentheses, close environments and generally demonstrate the superiority of free software.
Folding mode
Folding mode for emacs allows you to hide portions of a file to make it easier to read. It's similar to outline mode for Emacs or Word, but is more flexible.
You can get folding.el and find out more about folding mode at Anders Lindgren's Emacs page: http://www.csd.uu.se/~andersl/emacs.shtml#folding
Links
There's an Emacs wiki at http://www.emacswiki.org/cgi-bin/wiki.pl
See the WordCounts page for an emacs macro to count words.