To
node code, here's what I do:
<blockquote>
<pre>
[... my code goes here ...]
</pre>
</blockquote>
The <pre> tag ("preformatted text") puts it in a monospaced font and respects my whitespace, which is important for line breaks and indentation. The <blockquote> tag pushes the whole thing in from the margins a bit, and just looks a lot nicer.
You can see the effect on the HTML code above.
The Node Code