If you have the unfortunate pleasure of using WordPress for anything more than a simple blog, you’ll want to stick this in your functions.php and pretend WordPress is a good CMS. It isn’t, but you can pretend 🙂
remove_filter('the_content', 'wptexturize');
remove_filter('the_excerpt', 'wptexturize');
remove_filter('comment_text', 'wptexturize');
remove_filter('the_title', 'wptexturize');