Let's say you're using this HTML5 layout:
<html>
<body>
<header>
<nav><ul>...</ul></nav>
</header>
<article>
<ul>...</ul>
</article>
<footer>
<ul>...</ul>
</footer>
</body>
</html>
You could say in your CSS:
header ul, footer ul, nav ul { list-style-type: none; }
If you're using HTML 4, assign IDs to your DIVs (instead of using the new fancy-pants elements) and change this to:
#header ul, #footer ul, #nav ul { list-style-type: none; }
If you're using a CSS reset stylesheet (like Eric Meyer's), you would actually have to give the list style back, since the reset removes the list style from all lists.
#content ul { list-style-type: disc; margin-left: 1.5em; }