PluGeSHin is a Wordpress plugin that lets you use the syntax highlighting of  GeSHi through Wordpress shortcodes. This is a sample page. You can find full instructions on the PluGeSHin homepage. Remember that the look of this page will be affected by the defaults set on the PluGeSHin settings page. PRE tags that contain the highlighted code have the class name "PluGeSHin" to let you tweak the styling of your code blocks. Remember to use Shift+Enter if you're typing code and not pasting it in. You don't have to - PluGeSHin will still work if you don't - but it'll look nicer for you in the Visual edit screen.

Examples:

Highlighting using the default language (if you've changed your default away from "Javascript" the following may not look all that nice): 
[[geshi] CODE [/geshi]]
[geshi] 
$(document).ready(function(){
      // Create a selection of the content divs of interest
    var theDivs = $("#block-1-content, #block-2-content, #block-3-content");
      // Toggle the visibility of all divs when one is clicked.
    $("input.toggler").click(function() {
        $( "#" + $(this).attr("id") + "-content" ).show();
        theDivs.not( $( "#" + $(this).attr("id") + "-content" ) ).hide();
    });
});
[/geshi] The lang attribute let's you pick the highlighting language: 
[[geshi lang="html4strict"] CODE [/geshi]]
[geshi lang="html4strict"] 
<body>
    <div id="page">
        <ul id="menu">
            <li><a href="#">Home</a></li>
            <li><a href="#">Gnome</a></li>
            <li><a href="#">Rome</a></li>
        </ul>
    </div>
</body>
[/geshi] You can also show line number and draw attention to specific lines: 
[[geshi lang="php" nums="1" highlight="4,8"] CODE [/geshi]]
[geshi lang="php" nums="1" highlight="4,8"] 
<?php
class SumOfPower {
    function __construct () {
        // Start Timer
        $Timer1 = new CalcTimer;
        $Timer1 -> StartTimer();
        $number = sprintf( number_format(pow(2,1000), 0));
        for ($count=0; $count < strlen($number); $count++) {
            $digit+=$number[$count];
        }
        echo "The sum is $digit.<br/>";
        // Stop Timer
        $Timer1 -> StopTimer();
    }
}
?>
[/geshi] If you're showing line numbers, you can even start at a specific line number: 
[[geshi lang="lolcode" nums="1" start="37" highlight="3"]CODE[/geshi]]
[geshi lang="lolcode" start="37" nums="1" highlight="3"] 
ON CATURDAY
    IM IN YR BED
        I IZ SLEEPIN!!10
        VISIBLE "Z!"
    KTHX
KTHXBYE
[/geshi] Open links to the documentation in a new tab: [[geshi lang="php" target="_blank" ]CODE[/geshi]] [geshi lang="php" target="_blank" ] 
public function unload($name) {
    list($plugin, $name) = pluginSplit($name);
    if (isset($this->_loaded[$name])) {
        $this->_loaded[$name]->cleanup(ClassRegistry::getObject($this->modelName));
        unset($this->_loaded[$name]);
    }
    foreach ($this->_methods as $m => $callback) {
        if (is_array($callback) && $callback[0] == $name) {
            unset($this->_methods[$m]);
        }
    }
    $this->_enabled = array_values(array_diff($this->_enabled, (array)$name));
}
[/geshi]