John

This plugin enables you to highlight syntax using the PEAR Text_Highlighter class. Other syntax highlighters that use GeSHi have slower rendering speeds which will increase your page load time. However, this plugin gives you the speed and efficiency provided by the PEAR developers. You even have the option of enabling or disabling the line numbers as well as specifying your own style.

Ion Snytax Highlighter

This plugin allows users to highlight code.

FractalizeR

Plugin provides syntax highlighting in posts and comments.
<ul>
<li>Full GUI mode. No need to switch to code mode and back like in some other plugins</li>
<li>GUI editor with realtime syntax highligting support integrated (can be disable in settings)</li>
<li>GUI button to help with highlighting options. No need to memorize them!</li>
<li>Blog-wide default settings for code highlighting. Now you can change the look of all your posts at once!</li>
<li>Many options to customize code highlighting (almost full Geshi set)</li>
</ul>
If you like this plugin, you can make a donation with WebMoney (R704473788938, R704473788938), Yandex.Money (41001122895969), MoneyBookers (FractalizeR@yandex.ru)
<h3>Usage</h3>
Just select all your source code in the editor and use editor button (preferred method) or surround your code directly in WYSIWYG editor with a [codesyntax] [/codesyntax] tag like this
[codesyntax lang=”php”]
<pre><code><?php 
//Replacing tags
$find [] = '/<br\s*\\?>/i';
$replace [] = "\r\n";
$content = preg_replace($find, $replace, $content);
?>
</code></pre>
[/codesyntax]
[filesyntax filename=”test.phps” lang=”php”]
The tag in the last example should be enabled in settings. See it’s description below also.
and you will get wonderful geshi formatting. Format all your source code with Preformatted style to preserve spaces.
If you need to change settings of already formatted block – select it all and press GUI editor button again. Plugin will recognize all settings you used.
Plugin recognizes several popular geshi options to render highlighting:
filename
The relative filename of the file inside a folder, allowed for [filesyntax] tag to take the source for highlighting from. Works only in [filesyntax] tag
lang
The programming language you want to be your source highlighted in. [codesyntax lang=”java”]My java code goes here…[/codesyntax] 
The name of the language should match the name of the highlighter file. For the list of all supported highlighters please look at /wp-content/plugins/wp-synhighlighter/geshi/geshi directory of your WordPress installation after installing this plugin. A list of currently support languages:
abap, actionscript, actionscript3, ada, apache, applescript, <code>apt_sources</code>, asm, asp, autoit, avisynth, bash, basic4gl, blitzbasic, bnf, boo, c, caddcl, cadlisp, cfdg, cfm, cil, cobol, cpp-qt, cpp, csharp, css, <code>c_mac</code>, d, delphi, diff, div, dos, dot, eiffel, email, fortran, freebasic, genero, gettext, glsl, gml, gnuplot, groovy, haskell, html4strict, idl, ini, inno, io, java, java5, javascript, kixtart, klonec, klonecpp, latex, lisp, list.txt, lotusformulas, lotusscript, lua, m68k, make, matlab, mirc, mpasm, mxml, mysql, nsis, objc, ocaml-brief, ocaml, oobas, oracle11, oracle8, pascal, per, perl, php-brief, php, pic16, plsql, povray, powershell, progress, prolog, python, qbasic, rails, reg, robots, ruby, sas, scala, scheme, scilab, sdlbasic, smalltalk, smarty, sql, tcl, teraterm, text, thinbasic, tsql, typoscript, vb, vbnet, verilog, vhdl, visualfoxpro, winbatch, xml, xorg_conf, xpp, z80
lines
Do you want line numbers to be visible? Possible parameter values are:
<ul>
<li>no – no line numbers. [codesyntax lang=”java” lines=”no”]My java code[/codesyntax]</li>
<li>normal = normal line numbering</li>
<li>fancy – fancy line numbering 
This parameter defaults to fancy</li>
</ul>
lines_start
You can provide this parameter if you want your line numbering to start with a custom value. [codesyntax lang=”java” lines=”fancy” lines_start=”1000″]My java code[/codesyntax]. Please don’t forget to enclose a value into quotes exactly like in example 
By default numbering starts with 1.
container
You can select container, that your code will be wrapped in
<ul>
<li>pre</li>
<li>div</li>
<li>pre_valid</li>
<li>pre_table</li>
<li>none</li>
</ul>
By default pre is used. [codesyntax lang=”java” container=”pre”]My java code[/codesyntax] 
More information can be found in <a href="http://qbnz.com/highlighter/geshi-doc.html#the-code-container" rel="nofollow ugc">Geshi documentation</a>
capitalize
Do you wish your keywords to be automatically capitalized or decapitalized?
<ul>
<li>no – don’t change anything</li>
<li>upper – convert all keywords into uppercase</li>
<li>lower – convert all keywords into lowercase 
By default no change is assumed 
[codesyntax lang=”java” capitalize=”upper” lines_start=”1000″]</li>
</ul>
tab_width
If you want to change tab width, use this parameter: [codesyntax lang=”java” tab_width=”10″]
strict
This setting enables or disables strict mode for formatting complex pieces of data. Please see <a href="http://qbnz.com/highlighter/geshi-doc.html#using-strict-mode" rel="nofollow ugc">Geshi documentation</a> to find out more on the subject
title (new in 0.91)
This attribute sets the header of the collapsable code block (“Code” by default)
bookmarkname (new in 0.91)
The name of bookmark (Named anchor tag <code><a name="bookmarkname" /></code>) you want to refer to this codeblock. By default it is 
 codesyntaxX, where X is 1 for first code block on the page, 2 for second etc. You can refer to your codeblocks using hyperlinks 
 < a href=”#codesyntax5″>Link to fifth code block on the page or, if you used 
 [codesyntax bookmarkname=”fifthcode”] lang=”php” bbcode, you can then refer to this codeblock as 
 < a href=”#fifthcode”>Link to fifth code block on the page
blockstate (new in 0.97) 
Sets initial code block state when the page is shown to user. It can be default, expanded or collapsed. Default corresponds to expanded currently.
highlight_lines (new in 1.1) 
Provides a comma-separated list of lines, that should be specially highlighted in the code
doclinks (new in 2.3) 
Enables or disables generation of documentation links for keywords

WP-SynHighlight

Plugin provides syntax highlighting for about 116 programming languages via Geshi.

Ion Snytax Highlighter vs WP-SynHighlight