!Emacs 
Emacs is a wonderful program, which at times can seem daunting.  For a text editor, it is by no means a little program, the full install is over twenty megabytes.  It takes some time to get used to the interface, but once you do you'll never use any thing else for programming, writing HTML, marking up TeX documents. 
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Its main function is to parse Lisp AI programs. It is actually a Lisp interpreter. (Press ctrl-x e to find out what I mean)
!Installation
For windows, the program doesn't need to be installed as it is a precompiled binary.  Copy a shortcut to runemacs.exe and put it in the startmenu. 
!Shortcuts
You should learn how to use Emacs, here's everything I can remember off the top of my head. 
*Ctrl-x c   (closes Emacs)
*Ctrl-x k   (closes currently open file)
*Ctrl-x b   (lets you select between open files)
*Ctrl-x 2   (splits the window horizontally)
*Ctrl-x 3   (splits the window vertically)
*Ctrl-x 1   (puts window back together (keeps currently selected one open))
*Ctrl-g     (gets you out of jams)
*Ctrl-(spacebar)   sets the mark
*Ctrl-w     (cuts the text between the mark and where you are)
*Ctrl-y     (pastes)
*Ctrl-k     (cuts a line, multiple ctrl-k's stack the lines)
*Alt-x shell (opens up a shell)
*Alt-x goto-line  (lets you go to a specific line)
*Alt-x query-replace (lets you replace specific text with different text)
*Ctrl-x f   (lets you select a file to open, press enter to bring up a directory tree)
*Ctrl-s     (searches text for given text)
*Ctrl-x o   (switches between windows)
*Ctrl-x shift-6   (makes a window taller)
(Alt-x or esc-x let you type into the minibuffer, all the other commands start with ctrl)