While working on a project for a customer we had the requirement to display different parts of an exposed form of a view in different regions of the page. Additionally not all parts of the form should be visible on all pages of the site (i.e. the search box should be visible on all pages whereas other exposed filters or sort options should be visible on the result pate only).
Normally we would manage this by using some hook_form_alter()-magic and/or create a custom block with a coded form in it. But a hint of Daniel Wehner (dawehner) pointed me to a different solution:

drupal planet english