How to display code in blog entries?

I’d like to display code snippets in my blog as plain text. It keeps displaying as formatted HTML, for example <? echo "
<li>Howdy</li>
"; ?> will display as * Howdy.

Can someone tell me how to do this? I’ve attempted to use <PRE> and <TEXTAREA>, but <PRE> doesn’t work the way I want it to (<LI> still appears as a *) and <TEXTAREA> makes everything look really messy.

I’d like to be able to use: highlight_file or something, but it doesn’t seem like I can use PHP code within a blog entry.