Easy code highlighting for WordPress with Chili (the bundled version is 2.2):
code tab<code class="lang"></code> tagslang with the language to highlight<code class="php">echo "<script>alert( 'Hello ' + $name );</script>";</code><code class="javascript">alert( 'Hello ' + $name );</code><pre><code class="lang"></code></pre> tags if you want to preserve white space<pre> element to add line numbers