I was contacted by a web agency over the weekend to help add a 'search by location' feature to one of the client's website (CLS Group). The function of it was to show the location and area where their homes were located and provide information about the homes.
This was simply achieve using CCK and views modules, and the cool hierarchical select module. hierarchical select uses Jquery for a sliding effect to show multiple select group. You can see a working example at clsgroup website. The site runs on Drupal 5.