Odd functions.php issue in WordPress

There is no WordPress function called meta(). Try using get_post_custom() (Codex ref) instead. For example:

//Address
add_action( 'woo_post_inside_before', 'my_address' );
function my_address() {
    if ( is_single() && in_category('listings') ) { 
        global $post;
        $meta = get_post_custom();
        echo '<h1>' . $meta['address'] . '</h1>';
    }
}

Note: I’m not sure you need to call global $post; in this context?

EDIT: updated to add HTML tags.