hook_form_alter() exposed filter form item #weight
Take a look at comments #3, #7 and #9  in http://drupal.org/node/893392

#3 (dereine):


  The problem is that there is some theming on exposed form. You would have to override it, sadly.


#7 (manatwo):


  Yes, all of it is handled in views-exposed-form.tpl.php, which you can override in your theme to print out your fields manually. IIRC, the extra fields are gonna be in the $button variable in that template, so you might want to do some preprocessing in template.php


#9 (PadreHomer):


  I was able to alter the order without overriding the template. I am using Views 3, but I think this will work in Views 2 as well.
  
  Alter the order of the filters in $form['#info'] in your form_alter and this should alter the order the widgets print out in the template without having to do any custom templating.