daxitude

This plugin adds an advanced code editor to the post content box on post.php and post-new.php. A third tab is added alongside Visual and HTML modes and you can toggle between the three.
NOTE: Visual Mode tends to eat up most/all of any special formatting. If you want to use ACE I’d suggest disabling Visual mode completely. You can do this easily yourself under Users -> Your Profile -> ‘Disable the visual editor when writing’. You can also do it for all users and for specific post types only. See the accompanying file no-visual.php for an example.
Not all features work in Internet Explorer v8 and earlier.
This does not work in full screen mode. Yet.
<h4>Features</h4>
<ul>
<li>Syntax highlighting</li>
<li>Tabbing</li>
<li>Line numbers</li>
<li>Auto closing of tags and quotes</li>
<li>Line highlighting</li>
<li>Default theme is TextMate</li>
<li>Fixed-width, soft wrap, adjustable height</li>
<li>Remembers your last used mode and loads it up on initial page view</li>
</ul>
<a href="http://ace.ajax.org/" rel="nofollow ugc">ACE Editor</a> can do quite a bit more. If you have integration ideas, let me hear about it
<h3>Todo</h3>
<ul>
<li>make height of editor consistent when toggling between modes</li>
<li>deal with auto_p? (might help preserve formatting from Visual mode)</li>
<li>make it work in full screen mode</li>
<li>allow users to set their ACE preferences on their profile screen</li>
</ul>

ACE Editor for WP

Adds ACE Editor to the post content editor for syntax-highlighting and more

Bryan Petty

Adds line numbers, syntax highlighting, code folding, and lots more to the 
theme and plugin editors in the admin panel.
This plugin replaces the boring, clunky, and difficult to use theme and plugin 
editor with a full-featured code editor using the Ajax.org Cloud9 Editor.
Requirements:
<ul>
<li>Javascript Enabled (will use default editor if disabled)</li>
<li>Browsers: Internet Explorer 9+, Chrome 21+, Firefox 10+, Safari 6.0+</li>
</ul>
Included Themes:
<ul>
<li>Ambiance</li>
<li>Chaos</li>
<li>Chrome</li>
<li>Clouds</li>
<li>Clouds Midnight</li>
<li>Cobalt</li>
<li>Crimson Editor</li>
<li>Dawn</li>
<li>Dreamweaver</li>
<li>Eclipse</li>
<li>GitHub</li>
<li>idleFingers</li>
<li>IPlastic</li>
<li>KatzenMilch</li>
<li>krTheme</li>
<li>Kuroir</li>
<li>Merbivore</li>
<li>Merbivore Soft</li>
<li>Mono Industrial</li>
<li>Monokai</li>
<li>Pastel on Dark</li>
<li>Solarized Dark</li>
<li>Solarized Light</li>
<li>SQL Server</li>
<li>Terminal</li>
<li>TextMate</li>
<li>Tomorrow</li>
<li>Tomorrow Night</li>
<li>Tomorrow Night Blue</li>
<li>Tomorrow Night Bright</li>
<li>Tomorrow Night 80s</li>
<li>Twilight</li>
<li>Vibrant Ink</li>
<li>Xcode</li>
</ul>
Supported Languages:
<ul>
<li>ABAP</li>
<li>ABC Notation</li>
<li>ADA</li>
<li>ActionScript</li>
<li>AppleScript</li>
<li>AsciiDoc</li>
<li>Assembly x86</li>
<li>AutoHotKey</li>
<li>BatchFile</li>
<li>C9Search</li>
<li>C/C++</li>
<li>Clojure</li>
<li>Cobol</li>
<li>CoffeeScript</li>
<li>ColdFusion</li>
<li>C#</li>
<li>CSS</li>
<li>Curly</li>
<li>D</li>
<li>Dart</li>
<li>Diff</li>
<li>Dot</li>
<li>Elixir</li>
<li>Elm</li>
<li>Erlang</li>
<li>EJS</li>
<li>Forth</li>
<li>FreeMarker</li>
<li>Gherkin</li>
<li>gitignore</li>
<li>Glsl</li>
<li>Go</li>
<li>Groovy</li>
<li>HAML</li>
<li>Handlebars</li>
<li>Haskell</li>
<li>haXe</li>
<li>HTML</li>
<li>HTML (Ruby)</li>
<li>Ini</li>
<li>Jade</li>
<li>Java</li>
<li>JavaScript</li>
<li>JSON</li>
<li>JSONiq</li>
<li>JSP</li>
<li>JSX</li>
<li>Julia</li>
<li>LaTeX</li>
<li>Lean</li>
<li>LESS</li>
<li>Liquid</li>
<li>Lisp</li>
<li>LiveScript</li>
<li>LogiQL</li>
<li>LSL</li>
<li>Lua</li>
<li>LuaPage</li>
<li>Lucene</li>
<li>Makefile</li>
<li>MATLAB</li>
<li>Markdown</li>
<li>MaskJS</li>
<li>Maze</li>
<li>MySQL</li>
<li>MUSHCode</li>
<li>Nix</li>
<li>Objective-C</li>
<li>OCaml</li>
<li>Pascal</li>
<li>Perl</li>
<li>pgSQL</li>
<li>PHP</li>
<li>Powershell</li>
<li>Prolog</li>
<li>Properties</li>
<li>Protobuf</li>
<li>Python</li>
<li>R</li>
<li>RDoc</li>
<li>RHTML</li>
<li>Ruby</li>
<li>Rust</li>
<li>SASS</li>
<li>SCAD</li>
<li>Scala</li>
<li>Scheme</li>
<li>SCSS</li>
<li>SH</li>
<li>Smarty</li>
<li>snippets</li>
<li>Soy</li>
<li>SQL</li>
<li>SQLServer</li>
<li>Stylus</li>
<li>SVG</li>
<li>Tcl</li>
<li>Tex</li>
<li>Text</li>
<li>Textile</li>
<li>Toml</li>
<li>Twig</li>
<li>Typescript</li>
<li>Vala</li>
<li>VBScript</li>
<li>Velocity</li>
<li>XML</li>
<li>XQuery</li>
<li>YAML</li>
</ul>

Better File Editor

Adds line numbers, syntax highlighting, code folding, and lots more to the theme and plugin editors in the admin panel.

ACE Editor for WP vs Better File Editor