In the functions.php file find this…
if ( function_exists('register_sidebar') ) {
register_sidebar(array(
'before_widget' => '<li id="%1$s" class="widget %2$s">',
'after_widget' => '</li>',
'before_title' => '<h2 class="widgettitle">',
'after_title' => '</h2>',
));
}
And take out the list elements.
(You could go deeper down and have an if statement to just apply this to text widgets if you want)
