Change  class on one specific menu? I'd like to change the  class from "menu" on one specific menu I have showing up as a block on about 3 pages in a Drupal 7 site. I've been researching but can't seem to figure out the best way to go about doing this.
You can do this with theme_menu_tree() hook in your theme's template.php file.
Or with a more specific version of theme_mene_tree() hook like MYTHEME_menu_tree__MYMENU().  

function MYTHEME_menu_tree__MYMENU(&amp;$variables) {
    return '&lt;ul class="nav newclass"&gt;' . $variables['tree'] . '&lt;/ul&gt;';
}


See more here https://gist.github.com/gagarine/3201854

UPDATE:

if menu machine name have hyphne like main-menu then change hyphen to underscore, like MYTHEME_menu_tree__main_menu()